I think that the difference here is maybe whether college athletes are viewed fundamentally as kids who are developing a skill (which would be a pretty legit reason to insulate them within a limited age group, as high school sports governing bodies tend to do) vs being viewed as adults.
I tend to view them as fundamentally adults, which makes me see no reason to protect them from playing against older, potentially more physically developed players. But I also have 2 other reasons why I don't like the idea of imposing a maximum age. One is that some players may have to reach their physical peak in order to be able to compete at a college level. If there is a player whose talent maxes out at NCAA ability level, and he doesn't reach that level until he's 20 or 21 as opposed to 18, I can't imagine having a problem with that. Second, I suspect that there are a handful of players who, while playing in the Juniors have realized that they are not destined for the NHL. If, on the other hand, they can use the talent they do have to get a scholarship to pay for an education, I can't imagine thinking that should be taken away from them just because they aren't 18 years old when they make that decision.
False