@ct1417, my son’s former school also pumps a ton of kids into college. My understanding is most of the real elite hockey kids play juniors for a year or two before college. I assume that skews the numbers somewhat.
I think the NCAA is trying to account for some of the variation caused by the club system, which is why the data are in part estimates from surveys.
That said, certainly some sports are not included simply because of the limited pool of participants.
As far as crew, men’s crew is not an NCAA sport because of Title IX. Women’s crew is one of the few places where colleges can find a number of equivalencies to catch up with football. If a college sponsored a men’s team, at best you would have close to a set off and colleges would need to find another source to set off some of the 85 counters from football.