Similarly getting extra time on a test sure as heck would have improved my scores in many cases.

And ADHD meds seem like they would be helpful for studying.. How and where do we draw the line who gets and needs additional support?

I don't know about Stanford, but in earlier schooling accomodations can include things like being allowed to sit on a bouncy chair, or use a fidget toy, or type instead of hand-write (physical asynchronous development is a common issue), or wear headphones, or take more frequent breaks.

I do think that more flexibility in educational environments might be good for most people, yes.

100%, it's one of the irksome things about the education system in general - resources are limited. It's a hard problem to solve.