It doesn't matter why someone does it, having one's hands this close to the timer seems like it can lead to problems. As NigelTheCuber said above, apparently he has accidently wrist-stopped the timer before, which should be a DNF per this rule:
A6c) The competitor must fully release the puzzle before stopping the timer. Penalty: disqualification of the attempt (DNF)
I don't think anyone is cheating, but if something like this can lead to hard-to-detect early timer stops, it warrants looking into.