Yeah, it's a pointer which may happen to be a pointer to the start of an array ... or some other element of the array, or a different variable of the same type

Yeah, it's a pointer which may happen to be a pointer to the start of an array ... or some other element of the array, or a different variable of the same type (the type of the element), or a variable of a different type coerced into being passed as the right type. The compiler doesn't know or care! Do what you like! Hence it can't tell you the size of the thing because the thing could be anything and could have come from anywhere.