With the way they are banned, you see it only as a compiler warning on implicit declaration of function (or at linking stage, if warnings are suppressed; idk what exact build process is). Afair, there is no evidence of banned.h in an error trace. So you have to look it up by yourself anyway.

They could rename them as “sorry X is unsafe and creates too much trouble” maybe, but in today’s internet “X considered harmful” is a common search query that everyone in the field is expected to know.