When this change was made,I thought it might have been a way for the GB to solve the overlapping generation problem.
By removing the need for Armageddon to arrive before the anointed were gone, they could claim that the generation of anointed were still alive to witness the start of the great tribulation and be in heaven, ready to rumble, just in time for Armageddon
This could have allowed them to declare the start of the great tribulation and prolong it indefinitely, and, maybe buy themselves more time by keeping JW's in a heightened state of expectation. It would also remove the need to appoint ever younger men as GB members and use helpers instead.
Eventually, years later, when hardly anyone is alive that remembers 1914, they could reveal 'new light' in the form of a Christian death metal video, featuring an A.I. version of Stephen Lett, and start all over again.