It is a bug because there is a difference between the following cases:

    @skip("skipped")
    def test1(self):
        ...

    @other_decorator
    @skip("skipped")
    def test2(self):
        ...

    def test2(self):
        self.skipTest("skipped")
        ...

None is only returned in the first case. In other two cases a TestResult is returned with information about skipping.

It is obvious that it was unintentionally.

I just have fixed similar bug about calling stopTestRun() (issue44955).

Iman, please add tests and a NEWS entry. You can use tests added in issue44955 as an example.