Hey LL, haven't you and I discussed this before?
I agree that the CSM is a manager but doesn't the term 'Customer Service Manager' include the the term? Given that their title already has 'manager' part covered I'm still mystified as to why so many refer to themselves or others as the 'Onboard Manager'. It doesn't appear in the FAM, I can't recall it in the AEPM, I've never read it in Memos to Flight Crew or FSOs. The only time I've heard of the term is when CSMs use it to refer to themselves.
Anyway, good luck to them. Herding 21 crew to be aboard on time, etc is going to be like herding kittens.