Bottom line is that you'd have the right legal help that can dig through the pretext to the denial based on age. Schools can't denial d/t EEOC; but biased reactions occur all the time for all kinds of reasons. The federally protected blocking based on bias will not be listed, Eg., as Nas stated, "as old as dirt," or whatever.
Basically organizations can do whatever they want, so long as they don't get caught. Now, no organization really wants to deal with even a claim of discrimination based on EEOC issues. So they find ways to cover their tracks. Smart lawyers, however, can peel through the pretexts and makes strong arguments--and at the very least, give these schools bad press. So any youngster or older adcom member should really think more than twice about denying a seat based on age or EEOC issues. I mean they should think long and hard about avoiding them as factors--they should mentally put blinders on and not even look at the birthdate or age or color or whatever is protected under EEOC. In fact, go out of your way and just take it out of the equation, b/c that bias could get the school burned in one way or another.
Nas is just Nas, and there are those like him that are disenchanted about the whole MS/GME gig from start to finish. Their input, unless something dramatic causes internal changes within them, will continue to be on the negative side. Five years ago, he sung a different tune. I was here. I read it. He defended to some degree against age bias--and stated how youngsters w/o life experience are w/o some degree of advantage. He's entitled to change and sing whatever tune he wants. If he, however, decides to sit as an adcom member, sure, he might get away with quietly employing his biases--based on many subjective things from his own POV; but then again, he's taking a risk for the school and perhaps even for him.
Any school, whether osteopathic or allopathic, that is OK with its adcom members employing such biases is asking for trouble. The answer of course is that older non-trads have to go the extra mile, at least IMHO, unless they have the benefit of another URM status, to have super great applications (whole applications). The trouble is that for a number of nontrads, well, there may be some stuff from their earlier edu process that can be used against them, even if their more recent scholarship has been great. If someone is either consciously or subconsciously employing bias, do you not think they will use that?
The other things is that nontrads may not get exposure to research b/c of work and other responsibilities. So this can put them at the "right" 😉 disadvantage for non-acceptance at allopathic schools--wink, wink. There are any number of things in an application that can be used as a "non-biased" basis for discrimination--again, wink, wink.
All an applicant can do is her/his own due diligence in creating the very best application s/he can, and probably apply carefully to various schools. If Harvard is a reach for the 4.0 youngster with a +40 MCAT (or whatever the equivalent will be) and great ECs and solid research and LORs, it's a reasonable bet it will be even a greater reach for most non-trads.
The game is what it is. You do your best to have sound motives and play it as well as you can. But schools should be advised that there are great anti-discrimination lawyers that would be willing to take them on, and at the least, get them some very bad press. In fact, an older non-trad may well have nothing to lose in pushing this--even considering legal costs. If it is something they want to do, and they have a decent job and the money, they may be willing to push against it for years--at the very least--getting possibly some compensation, and at best, opening doors for other nontrads/those protected under EEOC.