Seems like a great idea!

Stirs up competition within a cohort and there’s bound to be idea sharing between teams. YC claims to bet on people not ideas, so as another commenter pointed out, if a team pivots there’s no longer a competition.

My guess is YC also believes in simultaneous invention: the same idea coming from multiple places at once implies said idea’s time has come, while any team wanting to work on it must have already done the work to hit that forefront, making them great people to bet on.