Variadic *args where args: Union[Tuple[...], Tuple[...], ...] are _never_ checked [False Negative]

[finite-state-machine]

Bug Report

When args is a Union of two or more fixed-length Tuples, and some_func() is callable, the following call is always accepted without error (regardless of what's in the tuples!):

some_func(*args)

To Reproduce

[mypy-play.net]

from __future__ import annotations

from typing import (
        Tuple,
        Union,
        )

class ClassA: pass
class ClassB: pass
class ClassC: pass

def some_func(value: ClassA, /) -> None:
    pass

u_bc: Union[Tuple[ClassB], Tuple[ClassC]]
some_func(*u_bc)  # expected: [type-arg]; got: no error

Expected Behavior

Mypy should notice that one or more of the Tuples that make up the Union are not appropriate for the callable, and complain about the argument types accordingly.

Put another way, mypy should examine each possibility posed by the Union in turn, and complain if any of them isn't suitable for the variadic call.

Actual Behavior

Mypy always accepts variadic arguments of this form, without any regard to the contents of the Tuples that make up the Union.

Your Environment

• Mypy version used: 1.9.0 (also checked 1.5, 1.0; this doesn't appear to be a recent regression)
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.8, 3.12