That is what is required under the DMCA, though. YouTube must remove content immediately after receiving a notice, under penalty of losing safe-harbor privilege

That is what is required under the DMCA, though. YouTube must remove content immediately after receiving a notice, under penalty of losing safe-harbor privileges. In turn, the claimant must represent themselves as the copyright holder or their agent, and the content must be infringing, under penalty of liability for the accused's costs and attorney fees. The law does not make a provision for YouTube to reject bogus claims.