I think it’s sometimes a little less than 15 depending on how much a coach uses his bullpen. But, yeah, that’s the reality of College Baseball.
The recently retired Tufts coach used most of his pitching staff. He was into opening pitchers and not facing any hitters twice before it was an MLB thing.
A friend’s son pitched there a few years ago. It drove him crazy to start, throw two shut out innings, get spotted several runs by his offense and get yanked.
But, even using five pitchers per game he still only used about twelve a week. About 22-24 players got “playing time” over the course of the season.