> Frontend candidates who have worked with CORS still aren't able to explain SOP and why those policies exist, in my experience

But that's exactly the kind of thing you want to surface in the hiring process with that question :) I guess it depends on if you're hiring juniors to be trained, or seniors to elevate your current team, but personally I'd skip very quickly on people who don't know the basics of their jobs, unless of course the point is to hire them to train them.