Also remember that most recruited athletes have already had positive pre-reads before they submit their applications. Iow, they have already been screened to be admits. If these were the only ones in the pool, the ED rate would be 100%. Some schools do a version of this with the kids of major donors as well.
There are LOTS of athletes who are advised not to apply and they go off looking for another school. So at the risk of being repetitive, these students who would not be admitted don’t get into the pool.
As for history with various high schools, I recall that kids in my son’s class were grumbling about an Ivy that "capped " acceptances from our school at 4 (with additional grumbling about how certain kids were going to grab those spots because of I don’t recall what.) 6 were accepted.
I think stories like @homerdog 's illustrate 2 things. Those unis consider the students from that high school adequately prepared AND it is extremely hard for unhooked kids (especially ones that share the demographics of athletes,
legacies, development cases) to get in period. They are not shutting them out because of the high school. It is frustrating, for sure.