What the function types are is vague

[xmh0511]

Call expressions - The Rust Reference says:

For non-function types, the expression f(...) uses the method on one of the following traits based on the function operand:

• Fn or AsyncFn — shared reference.
• FnMut or AsyncFnMut — mutable reference.
• FnOnce or AsyncFnOnce — value.

The non-function types, as indicated by the link, refer to function item types.
Consider this example:

unsafe fn foo(i:i32){}
fn main(){
  let f = foo as unsafe fn(i32);
  unsafe{
    f(0);
 }
}

f is of type unsafe function pointer, fn - Rust says:

In addition, all safe function pointers implement Fn, FnMut, and FnOnce, because these traits are specially known to the compiler.

The wording emphasizes safe; in other words, unsafe function pointers don't implement Fn, FnMut, and FnOnce. Furthermore, the (unsafe)function pointers aren't function item types, so why is f(0) a valid call expression?

More details can be seen https://users.rust-lang.org/t/why-can-the-unsafe-function-pointer-be-as-the-function-operand/133182