Probably not often because software companies don't care about PEs and because Stanford CS graduates are unlikely to apply for positions in non-CS fields (unless they also have an education in those fields).

But yes, there are a lot of jobs out there that even Stanford CS graduates aren't qualified for.

Note: the patent bar's eligibility rules have special exemptions for CS degrees that are not ABET accredited but do satisfy other criteria, so many Stanford CS graduates will automatically qualify for the patent bar based upon those alternative standards. But that doesn't mean the patent bar doesn't care about accreditation.

And it's worth noting that any institution with a half-decent reputation has some form of accreditation. Again, this was the second point of my post -- accreditation is actually does do a very good job at over-approximating the set of educational institutions whose degrees mean something.