RK, here is a post that has links to a good bit of research I have done on this parable (in case it is of any interest to you.).
There are numerous incongruities in the WT's explanation of that parable. For example, Jesus goes away at his death, with the promise of a return. But the WT explanation requires Jesus to return again in 1919 and go away again with a promise of yet another return.
The real and only reason for their present interpretation of this parable is that it suits them at the present time. The increase in Memorial partakers in recent times required them to react. They don't mind if most of the 'anointed' are already dead. But when there come to be many of them still alive they have to insulate themselves and their ruling authority.