Lots of funny comments on here. I watched the match, and saw the game. (I had no sound but could see the concession) Conceding a hill\hill match with 7 balls on the table is absolutely incredible to me. I do not care how good my opponent is, I'm watching that run out. Anything can happen.
Perhaps he was mad about not cleaning up. Perhaps he knew the other guy was out. Probably both true thoughts...but watch to see.
I am guessing Billy is kicking himself for that heat of the moment decision. I bet he does not do it again....
As for unsportsmanlike behaivor comments? No way. That was a concession of the match. No sharking, no bad behavior, just not a smart move imo...end of story.