I asked this a lot, and honestly loved these interviews and the conversations that stemmed from it. It turns out many candidates may work on either side of HTTP and be reasonably ok candidates who just happened to not be familiar with this part of the stack. Great candidates understood all this stuff, but not being good there didn't mean the candidate was bad, sometimes only that their strong suit was somewhere else. I think a good interviewer should be good at identifying that sort of "knowledge perimeter" where the candidate is strong.
A lot of this doesn't work with junior candidates, they just don't have the exposure to this stuff in school. Knowledge is really just one part of the equation too.
But what you can find out is that the candidate is honest and will tell you he/she does not know the answer.
In the end you want to work together on things and you want to know how the person ticks.
So a self reflected, honest candidate is good and at least I have the impression you can assess where you would need to provide support /trainings for the candidate, or how self learning would work
A lot of this doesn't work with junior candidates, they just don't have the exposure to this stuff in school. Knowledge is really just one part of the equation too.