Philosophically speaking, a claim and a rejection of one can often be the same thing. Both representing a philosophical position - Take for example, Nihilism, which is merely the rejection of all claims to intrinsic meaning, yet is also a distinct philosophical position. Anarchism, which is merely the rejection of any claims to authority via rejection of hierarchy itself. Tyranny, the rejection of the claim that the people should have the power. Democracy, the rejection of the claim that the king has power. Etc.
These can all certainly be framed as a rejection of a philosophy instead of a philosophy in their own right, yet if someone were to claim that anarchism wasn’t a position in and of itself they’d be wrong.