Back up. This is not all about stats. The issue is the kid with the 4.0 at a non-rigorous hs may not have had the same challenges, same higher expectations, as one from the more competitive. In some hs, you can find more general emphasis on, say, vocational electives than driving further in core subjects. Yes, it’s easier to stand out, when some larger percentage of seniors are not off to 4-year colleges. But that doesn’t speak for the readiness of this individual applicant-- not when you’re speaking of a highly competitive U.
The point is not college gpa. It’s the ability to keep up with more stringently prepared peers, in class, in the work, and prof expectations. So, the rest of the app matters much- how does “this kid” strive, how has he challenged himself beyond grades, what’s her potential impact? Does he or she seem to have the ability to self advocate? And so on. The teacher recs (and the quality of their observations) matter.
At the same time, when you assume kids at an underperforming hs can’t have the academic benefits, the stretch, the level of ECs, it ignores the individual and the picture that can come through. The picture in a tough holistic process.
GPA matters (as does course selection) because it shows this striving (for one’s top performance.) Scores matter because they show this same striving. But thay are not magic- you still need the rest of the picture. And that’s not just going for your own “interests,” walking your way through your hs experience. You can find the driven kids at a lesser hs. But this is about those individuals. Yes, I have admissions experience, not an adcom.
Be careful to try to understand from the front to back. Not back to front (or back-end,) which would be looking at acceptance and matriculation related info and assuming some things that may not be there. In general, top colleges care more about freshmn retention and grad rates than who gets what high college gpa.