Actually, the WTS has brought out that the WTS did not completely understand what 1914 meant until 1925. They tend to speak out of both sides of their mouth.
I remember when I read this in a 1993 WT and had seen the Proclaimers book which said they had believed the presence of Christ began in 1874. The following are those quotes and the ones about full understanding of 1914 not being until 1925.
*** w93 1/15 p. 5 ‘Caught Away to Meet the Lord’—How? ***TheWatchtower has consistently presented evidence to honesthearted students of Bible prophecy that Jesus’ presence in heavenly Kingdom power began in 1914.
*** jv chap. 28 p. 632 Testing and Sifting From Within ***Based on the premise that events of the first century might find parallels in related events later, they also concluded that if Jesus’ baptism and anointing in the autumn of 29 C.E. paralleled the beginning of an invisible presence in 1874, then his riding into Jerusalem as King in the spring of 33 C.E. would point to the spring of 1878 as the time when he would assume his power as heavenly King.
*** w97 6/1 p. 16 A Secret Christians Dare Not Keep! ***
1925 C.E.:TheWatchTower explains that the Kingdom was born in 1914; the "sacred secret" about the Kingdom must be publicized.—Revelation 12:1-5, 10, 17
*** w89 3/15 p. 15 par. 17 Look to Jehovah for Insight ***By means of "the faithful and discreet slave," Jehovah also helped his servants to realize, decades in advance, that the year 1914 would mark the end of the Gentile Times. (Luke 21:24, KingJamesVersion) As they entered the era following World War I, there were, of course, questions that perplexed them. But what they did know was sufficient for them to act wisely. They knew from the Scriptures that God’s due time was at hand for the old system to be destroyed; so it would be foolish to put their hope in it or to let its materialistic standards of success govern their lives. They also knew that Jehovah’s Kingdom is the real solution to all the problems afflicting humankind. (Daniel 2:44; Matthew 6:33) They saw clearly that it is the responsibility of all true Christians to advertise Jehovah’s anointed King, Jesus Christ, and His Kingdom. (Isaiah 61:1, 2; Matthew 24:14) In 1925, by means of the WatchTower article "Birth of the Nation," they were fortified with a clearer understanding of Revelation chapter 12; so now they understood what had been taking place in the heavens, invisible to human eyes. Such insight gave sound direction to their lives.
*** w86 5/15 p. 14 par. 17 "The Things Revealed Belong to Us" ***In 1925 God’s earthly servants became possessors of an accurate understanding of Revelation chapter 12 and discerned exactly what had happened in the marked year of 1914
*** w85 7/1 p. 20 pars. 8-9 Jehovah’s Goodness in "the Final Part of the Days" ***However, Hosea also foretold that these spiritual sons would "come back and certainly look for . . . David their king." Fleshly Israel has had no king since the overthrow of the Davidic dynasty in 607 B.C.E. That began 2,520 years of godless rule—"the appointed times of the nations," or Gentile Times. (Luke 21:24; Daniel 4:16) But in 1914, as "the final part of the days" began, God installed the One whom David typified—Jesus Christ—as King in Zion, the "heavenly Jerusalem."—Hebrews 12:22; Psalm 2:6.
Jehovah’s people on earth did not immediately understand all of this. However, their search for ‘David our king’ was climaxed when TheWatchTower of March 1, 1925, published the article "Birth of the Nation." This set forth conclusive proof, based on Revelation chapter 12, that Jehovah’s Messianic Kingdom had been born in the heavens in 1914 and that Christ is now ‘ruling in the midst of his enemies.’—Psalm 110:1, 2, KingJamesVersion; 2:1-6.
*** w84 2/1 p. 23 par. 9 ‘Oneness of Spirit’ in a Rapidly Growing Flock ***In modern times, Jehovah has continued to provide needed help for his servants, doing so through "the faithful and discreet slave," the remnant on earth today, of which Jesus is the appointed head, and this help comes at just the right time. (Matthew 24:45-47) Thus in 1925 the "slave" class, by means of TheWatchTower, helped its readers to appreciate that God’s Kingdom had been in operation in the heavens since 1914 and that, in reality, there are just two organizations—Jehovah’s and Satan’s.
*** w81 5/1 pp. 26-27 par. 17 The Visible Part of God’s Organization ***Back, however, to the meaningful year of 1925. The long misunderstood vision of Revelation 12:1-17 was cleared up. The March 1, 1925, issue of the WatchTower magazinecleared away the idea that the birth of the man-child by the "woman" in heaven pictured the birth of the papacy from an apostate religious system during the fourth century. Rather, the bringing forth of the man-child portrayed the birth of God’s Messianic kingdom from his "woman," his wifelike heavenly organization. This took place in the heavens at the end of the Gentile Times, "the appointed times of the nations," in the autumn of 1914 C.E. The earthly part of Jehovah’s spiritual organization was thrilled at this revelation!
*** w55 6/1 p. 335 Part 11—Restoration of Theocratic Organization ***Nevertheless, 1925 turned out to be a marked year in that a flood of new spiritual truths came to Jehovah’s people. It was in this year that TheWatchTower brought them the sublime revelations that the name of Jehovah must have its proper place; that the birth of the man-child Kingdom organization occurred in 1914; that Satan had been cast out of heaven and now must confine his operations to the earth; that Jehovah purposes to make a great and lasting name for himself at the battle of Armageddon; that such battle is not a fight between capital and labor, conservatives and radicals, or by any human parties and nations, but is God’s fight against the entire Devil’s organization, invisible and visible; and finally, that Jehovah’s servant class on earth have no part in that fight, but must only warn of its coming.
*** w51 7/15 p. 435 par. 11 The 1,290 and 1,335 Days of Daniel’s Prophecy ***Furthermore, in 1925, for the first time, it was seen and understood that the Kingdom was actually born in 1914, that it was a fact. No longer was it a matter of proclaiming the time had come for the Kingdom, that the day was here for Satan’s world to end, but the Kingdom had come and was ruling from heaven, and already a war in heaven had been fought. TheWatchtower for March 1, 1925, published this information
*** jv chap. 10 pp. 138-139 Growing in Accurate Knowledge of the Truth ***However, at that time the Bible Students felt that the setting up of the Kingdom, its fullestablishment in heaven, would not take place until the final members of Christ’s bride were glorified. A real milestone was reached, therefore, in 1925, when TheWatchTower of March 1 featured the article "Birth of the Nation." It presented an eye-opening study of Revelation chapter 12. The article set forth evidence that the Messianic Kingdom had been born—established—in 1914, that Christ had then begun to rule on his heavenly throne, and that thereafter Satan had been hurled from heaven down to the vicinity of the earth.