Could it be that your publisher has licensed music (that they have rights to) to a YouTube client (artist) only to discover that the music has been entered into YouTube’s CID program generating a claim? The link provided says YouTube requires writers/composers who tag a piece for CID monitoring must have exclusive ownership of the music, writer side and publisher side you would assume. Sounds like they’re taking it all down and putting it on the originators to upload CID free music to 1.) avoid claims, and 2.) ensuring rights splits reflect current ownership. The implication from your publisher also seems to suggest that some of this music has a convoluted rights pedigree at best, or at worst, someone is trying to claim music they don’t own.