The way that rust attempts to prevent this class of error is not by making an implementation of free that is safe to call twice, but by making the compiler refuse to compile programs where free could be called twice on a pointer.

Anyway, use after free doesn't depend on a double free. It just means that the program frees memory but keeps the pointer (which now points at memory that could contain unrelated data at some future point in time) and if someone trying to exploit the program finds a way to induce the program to read or write to that memory they may be able to access data they are not expected to, or write data to be used by a different part of the program that they shouldn't be able to

I loath it and the only thing I would think if someone called me it is that they have an uncomfortable fixation on my height. I think at the very best it is obnoxious.

Hollow Knight is pretty different than metroid games and I'm not sure I'd directly compare them. I'm the only person I know that doesn't like Hollow Knight and it seems like the departures it makes from the classic metroidvania formula that put me off it are part of the reason other people like it