Agree with your post, but want to clarify what we mean by squandering talent.
For the past few years I have coached several elite high school athletes who went to college track powerhouses. The ones who were nearest their limits before going to college tended to improve very little, if at all, while those who still had a lot of room to improve tended to do so, as one might expect. Most college coaches didn't seem to do their homework about this- they looked only at performance, not potential. (Texas Tech was a notable exception)
In the case of Cal and the University of Florida, the athletes they got from us were very near their limit coming out of high school, so I can't blame the college for their failure to improve. By contrast, one of our athletes with a world of potential went to the University of Oklahoma and made continuous, substantial progress.
One of the best athletes I coached, however, who still had huge upside coming out of high school, went to the University of Texas, started poorly and got worse every year. That's my only personal experience with a college truly squandering the talent of an elite high school athlete.
I pointed out on another message board at that time that this was the third year in a row that Texas' #1 recruit in this event group (horizontal jumps) had flamed out, and another poster retorted: "It's hard to recruit female jumpers."
(In fairness it should be pointed out that this occurred before Coach Floreal was hired. Texas did a decent job this year of not squandering the talent of our #1 all-time best athlete, although she was a bit tired out by outdoor Nationals.)