Type not narrowed on `isinstance(obj, Callable)` check

I received this bug report from a pyright user: https://github.com/microsoft/pyright/issues/2274. Mypy exhibits the same behavior, so I'm wondering whether it's a bug or the intended behavior.

In this code sample, mypy (and pyright) do not currently narrow the type of obj based on the isinstance(obj, Callable) conditional check.

from typing import Callable, Union

def some_func(obj: Union[Callable, int]):
    if isinstance(obj, Callable):
        reveal_type(obj) # Type of "obj" is "(*args: Unknown, **kwargs: Unknown) -> Unknown | int"
    else:
        reveal_type(obj) # Type of "obj" is "(*args: Unknown, **kwargs: Unknown) -> Unknown | int"

I'm wondering if there's a reason why mypy does not perform type narrowing in this case. Is there a type safety reason? Is callable() the preferred way to check for callables?

I've searched the issue database, and it doesn't appear to be an issue that anyone has previously reported.

Start by running the Python reproducer with mypy and checking the revealed types for both branches. Trace the existing isinstance and Callable narrowing behavior, including any related tests or documentation. Done means establishing whether this behavior is intentional and, if it is a bug, defining a tested narrowing result.