I don't quite understand what you mean. WCMD_ReadFile is called directly/indirectly in a lot of places, mostly around line-by-line reads. The question is not whether the compiler will inline this function (you can't know that for sure, think -O0, different compilers, etc.), but whether you want to check that every time.
This function is_console_handle() could be inlined or not/fast, but that's not the point. The point is why would one want to run that function when not necessary, i.e. when callers already know the type. It's just about finding/detecting the handle type once and only once (per handle).
the point is about passing twice the information to a given function the point is about adding unnecessary enums that clutter all the code the point is about thinking that you're only computing once a value, while you still need to compare the handle type (as you added it) to a given number A+