As near I can tell, 99/100 there is no intent to the hand ball. But refs have to make game changing hand ball calls based on supposed intent because if they didn't, then players would in fact start leaving their arms all over the place as an added "accidental" obstacle. So we go on pretending a player meant to put his arm somewhere to block the ball, ignoring the fact that no one at that level would think they could get away with it, when really he was just trying to keep his balance.
Disclaimer, I didn't see the play you were talking about.