I think you are in danger of being sidetracked from your title question Gary.
If I claimed that God chose me for a particular role in say , 1962, I could not play you a recording of his voice telling me, so I would have to offer different evidence, if I wanted you to follow me, trust me, believe my interpretation of scripture, and remain loyal to me etc etc
If I claimed to be "God's channel of communication" I would point to all the correct directives on matters I had given you since 1962, all the correct biblical interpretations of prophecy since 1962, all the good works I had done in looking after things that would be expected of me in the God appointed role.
In particular, I would point to one unique doctrine that I was teaching, in 1962, that proved my claim for that year, nothing less would do, later teachings and works have no bearing on that year.
This evidence would be good enough to convince a Court of Law and would withstand any scrutiny.
I am sure Bro Hero will be able to do this for his claim of the 1919 choosing of the Bible Students.
Let us know his evidence so we can put trust in that claim too !