True, not all ED/SCEA/REAs admitteds are hooked.
However, at the tippy top colleges, ED for unhookeds doesn’t give much of a boost anymore. When you strip out the athletic recruits, legacies, developments, URMs, and other institutional priority admits, there are very few ED spots left. For the unhooked in ED at ultra-rejective schools, the acceptance rates aren’t very far off what the acceptance rates are for Regular Decision. Some BS counselors will actually tell kids they have a better shot in RD than ED at certain elite schools. From what we’ve seen, the few ED spots left go to sky-high stat and class rank kids.
ED still does provide a significant boost for unhooked kids at most LACs.
As mentioned by several here, Chicago is an outlier, which continues to admit unhooked kids in ED and ED2 rounds at much higher rates than its peers - even those that don’t have super-high stats.
The Harvard Westlake handbook that was uploaded here in the forum gives great insight into unhooked acceptance rates, along with GPA buckets. The HW data is a great proxy for BS kids.