Hot take but I will go as far as to say for every single fastball thrown across D1 baseball it's probably a 60/40 split above/below 90mph. This is by individual pitch, not pitcher.
In other words if 300 pitches are thrown in any given D1 game, I would put my money on there being about 120 below 90. Now when Florida plays Vanderbilt where likely won't be a fastball below 92, but there are plenty of games that may not see a fastball above 88 as well. Even the guys who touch 90/91, they will largely be 88/89. 87 is more common than 95.