Now please explain to me how C works.
That's not what they're asking. It's not about how C works, it's about how specific APIs written in C work, which is hard to figure out on your own for anyone who is not familiar with that specific code. You'll have to explain that to any developer coming new into the project expected to work with those APIs, no matter their experience with C.
Eh, that's a bit of a stretch. There's more awareness by default here because of GDPR and such, but I wouldn't say people really care that much more here