I've been thinking about this and really am seriously considering the option that they did this to move some of their end time theology around. Somehow keep 1914 as a significant date, perhaps still the start of the last days but push all that 2 witnesses who are killed, trumpet blasts and other things that they've said has already been fulfilled to a more modern date to coincide with the appointment of the GB in the early 70s. They could say the Franz defection was the evil slave.
I'd have to sit down with all the things they've said has already been fulfilled in the early part of the last century and map it over to the later part of the last century but since their first interpretation is made up, doing it again should be that hard.
I can't think of any other reason for them making this change. After all, the other "annointed" have already been marginalized and aren't important. They're so small in number and most have a huge lack of standing in the organization that they're hardly a threat to the power structure. So, its not like they're pulling a coup since they have all the power and control anyway.
If I get insipred, I'll pull some information and see if I could put something together. Of course, its a complete waste of time....