The Society has never made any non-trivial predictions, or even non-trivial interpretations or misinterpretations of the Bible, that came true.
For GermanJW, Knorr's "prediction" was derived from his reading of newspaper accounts that also "predicted" that WWII would end in victory for the Allies. Also remember that this new idea reversed the Society's many "predictions" under Rutherford that Armageddon was near and that WWII would lead directly into Armageddon.
For nytelecom, the Society has indeed made predictions. A dishonest apologist might attempt to argue that because WTS leaders do not claim to originate these predictions in the sense of interpreting events, they're not really making predictions. But whether someone makes predictions based on interpretations of events, or of the Bible, or on anything else, they're still making predictions. A prediction is simply a statement of what is supposed to occur in the future. What the Society has done is to mix up its own interpretation of the Bible with its own interpretation of events, such that trying to make a distinction is completely useless.
What sort of predictions did the Society or its founder C. T. Russell make based on misinterpretations of the Bible and of events? Here is a sample:
(1) That "the saints" would be resurrected in 1881. This was based on false chronological interpretations and so forth, coupled with current events like the depression of the 1870s and the rapid pace of world technological development.
(2) That the final destruction of the nations would begin to occur as early as 1904. Same basis as above, reinforced by the depression of the early 1890s.
(3) After 1904 that the destruction of the nations would begin around 1910. Similar basis as above.
(4) After 1910 that the destruction of the nations would begin around 1914 or 1915. Similar basis as above.
(5) After 1914 that the destruction of the nations would end around 1918. Similar basis as above.
(6) After 1917 that Armageddon would begin around 1920.
(7) After 1918 that Armageddon would begin in 1925.
(8) After 1925 that "the ancient worthies" such as David and Samuel would be resurrected Real Soon Now. Again the current events of the 1920s were used as justifications for the false predictions.
(9) Until Rutherford's death in early 1942 that Armageddon was Real Close Now, -- in 1941 just "months away".
(10) Until the mid-1950s that Armageddon was still coming Real Soon Now.
(11) Beginning in 1966 that Armageddon was virtually certain to come by 1975. Again current events were massively played up as proof that "the end" was so close.
(12) Various suggestions in WTS literature of the 1980s that Armageddon must come by 2000 (or the turn of the century). Again the justification was "how bad this old world is and so it can't last much longer".
(13) Many positive statements in post-1990 WTS literature that "the end" is Real Close Now, along with claimed explanations of why both the Bible and current events prove it.
As for the claim of WTS leaders that they and the JW community comprise several sorts of "prophet" groups, during Rutherford's day that was taken in the usual sense of "prophet", since the Society claimed that its predictions based on the Bible and current events were sure. After so many predictions fell flat, the Society gradually began suggesting that a "prophet" is mainly someone who teaches God's truths. But of course we know that by this measure too, WTS leaders are "false prophets" because they teach and have taught so many false things about God and in God's name.
As has often been pointed out, Watchtower leaders want the honor given to a true prophet of God, but not the responsibility. This is proved by their continual attempts to cover up their massive failures both in prediction and in teaching.
AlanF