Not necessarily. At least for writing gigs my wife has done, often they involve assigning all rights but not ownership to the client. This is spelled out in the contract, I imagine to avoid controversy over whether there was "work for hire" or not. On the other hand, every dev job I've taken has had me sign a thing saying that the work I do is work for hire and the employer owns the copyright. Seems fair, they're giving me a paycheck after all.
Would this artist have made any money if they had assigned all rights and not ownership to the client? No.
So what's the difference?
In practice, none. I just think contract law is interesting.
unless it can be inserted into a handshake agreement, that's not really relevant to this case.