[singleshot_]

When people say "they don't know the difference between an A and a CNAME" they're not just talking about the basic definition of these concepts, which I agree with you is trivial.

But can you remember _which is which_? For instance, can a host have two A records? Can a host have two CNAMES? one of these might mess with mail delivery but the other is pretty common. Do you remember which is which?

DNS is an onion. At first it makes tons of sense. Then you learn a little bit and it makes less sense. Then you learn some more and it makes more sense. It is a bit tricky like that in a way that trips up lots of people. This speaks a little bit to your "levels of engineers," I think.