Swimming I'll buy, although several of the best females actually hit it big at the Olys while still in HS (Missy Franklin and Katie Ledecky being just the 2 most prominent off the top of my head from the past 2-3 Oly cycles; they were already multi-medalists before going off to Cal & Stanford), and some of the best men like Phelps either skipped college entirely or dropped out pretty quickly to just focus on swimming full-time. The real truth is that most of their training & development credit should go to their private club programs. Diving maybe, I don't know enough to comment.

Track & field might seem like it, but if you pay closer attention there really aren't many that reach the Oly level while still training & competing within the collegiate system; my alma mater is one of the perennial T&F powerhouses, with multiple Olympians among our alumni (both US and foreigners who went to skool here), and yet I can think of scarcely a handful that did so before graduating or leaving early to turn pro. It's true most of the eventual Olympians did come through the NCAA ranks at some point so there's obviously some benefit/credit there, but most of them still have a few more years to go after that. If you look at the avg ages, most of them are mid-20s or older:

https://www.si.com/...track-and-field-team

And those are the sports that seem like the obvious choices; perhaps wrestling or water polo too, maybe? But then what about Badminton, Shooting, Luge, Ski Jumping, Equestrian, Gymnastics, Taekwondo, Boxing, Archery, Curling, Speed Skating, Fencing, Canoe/Kayaking, Synchro Swimming, Cycling, etc, etc...? I'm just not seeing any sort of Oly-level development pipeline coming out of college for any of those. Either they're club-level sports (i.e., not elite/scholarship level) or sports like gymnastics where their Oly window has already passed by the time they reach college age. I think Ken's take is pretty well on the money ~ just because those same sports exist at the college level doesn't mean anywhere near "most" Olympic athletes are making it based off a collegiate program.