Good points, and that's why I wanted to ask about it.
A while back I went to train with a PL coach who's a Metal Militia (CPA) member and owns the Montreal BB Gym. I helped out on a few meets with him and two competing PL's I know train there on a regular basis.
Needless to say these guys have a lot to offer in terms of advice and proper technique. I went with my friends on their Bench Night and took the opportunity to learn this coach's technique, hit a PR right then and there.
All this to say that this guy, and subsequently everybody he trains for competitions including my friends, all swear by the full grip. My good friend, who had been training thumbless for years and got to a 480 bench this way, has since changed his technique.
From what I understand, the reasoning is due to safety more than anything else.