To get back on track to the original question, the thing that always made me suspicious of the GB interpretation of Matthew 24:45-47 is that they have always stated that Jesus' warning of an "evil slave" in the rest of the chapter was not literal - that he was not saying that there was a risk the "slave" could turn bad.
That appears to completely contradict the pattern set by all the other parables and illustrations Jesus gave. Wheat and weeds, sheep and goats, broad road and narrow road, wise virgins and foolish virgins, house built on rock vs house build on sand, etc - every one of those was a warning of the potential or danger of choosing to be on the wrong "side" by making bad or foolish choices. Yet mysteriously, the one parable that did not contain that message is the one about the faithful slave? How convenient.
Oh no, they say - the "slave" has proved itself faithful and so could never turn evil!
Then what was the whole point of the illustration in the first place? Jesus was clearly warning the "slave" (whether we identify the slave as an individual or a group - and that's another question) that he/they could go either way: do as the master wanted and be faithful, or become lazy and arrogant and "beat their fellow slaves", for which they will be later judged as "evil" when the master returns. There is no lesson or warning and the whole thing becomes pointless if there was never any risk or chance that the "slave" could become corrupted or turn evil.
Instead, the clear warning is that anyone wishing to identify themselves as that slave MUST be doing what the master wants in serving the "household", or risk being judged "evil" on His return. But no, that's too stark a message for the GB to tolerate and it would hold them too accountable for their liking, so they choose to claim the master has already come, observed them and declared them faithful - with no real scriptural proof, and in a way that is very dangerous to presume. By disregarding Jesus' warning and claiming he has already returned and declared them righteous, they in fact make themselves even more likely to be identified as the "evil slave", because it makes them too self-confident and presumptuous of their own position. and adamant that the Master will bless them when He returns "in Kingdom power"!
It also interestingly parallels Matthew 22:11. where a wedding guest presumes he's entitled to be at the feast, but is thrown out by the King at the last minute when He arrives and finds the guest not properly 'dressed'. There is a presumption among JWs, from the top downwards, that all GB members (and anyone else declared 'anointed') are definitely heaven-bound and certain to become part of the Bride of Christ, even though that privilege is not for men to claim, but only God. (That also links to my view of the GB interpretation of the 144,000 too, which is being discussed on this thread).