I agree with you that there is a lot of self-selection in match lists, and not only in terms of geography. And I'm actually perfectly fine with people disagreeing and finding flaws in my algorithm, because I use match lists more as a confirmation that "oh yeah, if I do my best here, I won't be restricted in what I want to do and where I want to go" than a basis for school selection - in fact, I'm not even sure I've seen match lists of all the schools I interviewed at, let alone all the schools I applied to. But I believe my algorithm for a single specialty is still valid
Re: school selection and whether school matters in residency applications:
isn't this a good reason to choose a bigger/more established etc. school? 1) You get exposure to more specialties - you may end up loving a specialty you never even considered before medical school. 2) You can get a nice LOR for that specialty and may have a leg up with your application for your home program.
(just thinking out loud)