You are missing a HUGE piece of the puzzle and thats transfers. Most of the pure hockey schools bring in a bunch of stud kids during their junior or senior seasons. Look at Cushing and Thayer - they bring in tons of kids later on. Some schools such as BB&N don't do that. They rely on the kids they brought in when the kids enrolled in 7th and 9th grade and you are stuck with those kids. Kids can't just transfer into BB&N and play hockey. Its a school policy. Belmont Hill and Sebs are similar. Those school can't rely on bringing in transfers and thats a huge handicap when trying to build a hockey super power.
What do Junior and Senior (and PG) transfers have to do with a coach actively recruiting Freshmen and then not being able to even get them into the school?
If a coach at Cushing or Thayer brings in Upperclassmen and takes minutes away from a Sophomore, at least the kid's still in the school enjoying the benefits of the education. Chances are the kid hasn't developed and isn't tracking the way the coach projected when the kid was 14. Again, though, that's an NCAA mentality on display.
It shows how difficult it is for schools that don't accept transfers. They have to get it right the first time and admit kids when they are 13 and hope they develop. Other ISL schools can cancel out their mistakes by bringing in transfers. Huge difference in recruiting.
Schools prioritize in different areas - BBN prioritizes itself on academics and has more stringent admission standards than Cushing or Thayer. Level of expectations should be different as well. Look how BC Football struggles compared to Alabama where they let in any good athlete.