What an absolute load of nonsense on this thread...
What does it say in the FCOM limitations?
Is the B757 certified for backing up using reverse thrust or not?
YES or NO
If yes, then fine, no probs..
If no, continue to the end, use the approved turning dumbell..
Getting into the who, what, why, when, how is irrelevant..
Just operate the jet in the approved way..
End of story