I believe they are DMCA claims. The exist because it grants youtube imunity in the process. Youtube had no incentive to get involved except for pissing off their content creators. If you can't counter claim/sue then get loud. Let your viewers know.

Edit: reading in another thread that perhaps this is content ID. Not that, that is any better.

After 2 "appeals" adjudicated by the original claimant, YouTube requires the original claimant to file a DMCA claim. But before this, no.

No, they are "copyright takedown requests"

They don't say that they are DMCA claims, but they are DMCA claims.