I think it's a shame that this solve was disqualified. (-1,0) is not a full move according to the regulations, and in any case the move didn't make the solve easier in any way.
Disqualifying the solve after the fact based on video evidence is well within the board's rights, and while I think it's a bit annoying, I can't really argue with that. However, I stand by my judgement that this was NOT a move, and should not be penalized.
A bit of anecdotal evidence: I myself have done this exact sort of thing many times. I have also, repeatedly, received square-1s from the scrambling table in an "untwistable position" (meaning that a turn like this was made by the scrambler, runner, or judge before it got to me). My action in these cases has always been to leave the puzzle "as-is" (as Kunaal did) to avoid making any intentional moves, and I have never once been penalized. Now this is beginning to cause doubt: what should I do in a situation like this to avoid a penalty?