Wouldn't bolting after the class is signed be worse? Doesn't seem like a good time to leave a team on good terms in that regard.
There's never really a good time to leave other than announcing before the beginning of the season that you are leaving after the end of the season. Just before is certainly worse than just after. Yes, a kid can freely leave if the coach who just signed him leaves but with the newer transfer rules they can leave with no pain. I just think that a kid is more likely to stay if he signs than if a coach gives him an out just before he signs. Most of the top players signed in December but they can leave just as easily as the remaining kids who sign next week. I think if he is leaving that trying to time it where he is least hated for it by the fans is a factor.