I DO think that ED is, and always has been, helpful in getting the full pay students.
At the school my son attended, many students who need aid also do ED – IF the NPC shows it will be affordable. They are, of course, giving up the opportunity to see if somewhere else might be more affordable. But the full pay students are giving up the chance to see what kind of merit they could get elsewhere. ED does not allow optimization for anyone. But if it gets you admission where you can pay it, it works.
Programs like Questbridge also use ED spots. As noted, not all buckets are the same!