Perhaps these unknown siblings were created because there is a record naming them without names. For instance, some church records will mention the death of someone, with the note: leaving behind 4 children. Or there's an obituary that mentions: the oldest of three children. That might be the clue that these unknowns actually existed, but there's no name for them.
Since you mentioned the PM is still active, I would send them a note asking them for their reasoning behind the unknown profiles. And maybe work with them to try and name some of them. Even if the unknown profiles are not based on any sources, there might be siblings, and you might be able to name them. That would be better than merging them away, only to have to make new profiles.