It is evident that the WTS has altered its view several times on when God chose it as his channel. On none of those occasions has it declared that it was a change of doctrine; one date simply supplanted another.
So when did the inspection and selection take place? Take your pick:
(a) 1879. (After discussing an 1882 Watchtower that discussed God's name and identity): "In many ways the evidence was beginning to accumulate that, of all the early voices heard, Jehovah had chosen the publication we now call The Watchtower to be used as a channel through which to bring to the world of mankind a revelation of the divine will and, through the words revealed in its columns, to begin a division of the world's population into those who would do the divine will and those who would not. For this reason 1879 was a turning point in the work. This little group, headed by C.T. Russell, had now been tested and had been found fit to undertake the great preliminary campaign leading up to the climax expected in 1914." (Jehovah's Witnesses in the Divine Purpose, 1959, page 22).
(c) 1914. "Whom did Jesus appoint to feed his followers in the first century? And whom did he find still faithfully doing so when he returned in Kingdom power in 1914?" (Organized to do Jehovah's Will, 2005, page 16). "On his return in Kingdom power in the year 1914, did Christ find a “faithful and discreet slave” class providing spiritual “food,” or information? Yes, he found such a “slave” made up of the remaining ones on earth of his 144,000 “brothers.” And since 1914 millions of persons have accepted the “food” they provide. (Live Forever, 1989, page 193).
(c) 1918."In 1918, when Jesus Christ inspected those claiming to be his slaves, he found an international group of Christians publishing Bible truths for use both inside the congregation and outside in the preaching work. In 1919 it truly turned out to be as Christ had foretold: “Happy is that slave if his master on arriving finds him doing so. Truly I say to you, He will appoint him over all his belongings.” (The Watchtower, March 15, 1990, page 14). "Thus, when the Lord’s day dawned in October 1914, there were still true Christians on earth. It appears that Jehovah came to his spiritual temple for judgment about three and a half years later, in 1918, accompanied by Jesus as his “messenger of the covenant.” It was time for the Master to reject finally the false Christians and to appoint ‘the faithful and discreet slave over all his belongings.’" (Revelation: Its Grand Climax, 1988, page 31).
(b) 1919. "Since the 'master' found the remaining ones of this body faithfully and discreetly giving out 'food supplies' when he arrived for inspection in 1919, he appointed them 'over all his belongings.' The facts show that since 1919 this 'steward' has faithfully cared for these 'belongings'." (The Watchtower, September 15, 1983, page 19). "When the enthroned Lord Jesus inspected his household in 1919, he found the group of Christians associated with the Watchtower magazine loyally striving to “keep on the watch” with the help of spiritual “food at the proper time.”" (The Watchtower, December 1, 1984, page 17).
For a religion that insists it knows the truth, and needs to nail down every specific detail of it, this is a pretty extraordinary trail of evidence. Did anyone in the org notice? Did anyone care?