But what if the limiting factor of admission criteria isn't scoring well but things like crippling amount of debt, archaic culture of hazing and adversity to stupid hours?

Right. Are doctors ubermensch who are the cream of the crop or did they just have a high tolerance for abuse? I’m not sure being ultra-selective gets you people who are fundamentally better doctors nor are the returns gonna be very linear even if they were. I’d much rather have enough well-rested doctors than have more “select” but highly stressed, sleep deprived doctors.

you're kind of assuming that the metrics that the use to admit students are predictive of care quality. thats certainly not true, but who knows how not true?