Why should @overload need to be followed by an implementation when an implementation already exists in the parent class?

Illustrative example:

class Parent:
    def foo(**kwargs):
        """Argument names of foo vary depending on the child class."""

class Child(Parent):
    @overload foo(a, b): ...
    
Raises:

"NotImplementedError: You should not call an overloaded function. A series of @overload-decorated functions outside a stub module should always be followed by an implementation that is not @overload-ed."