With regrds to the terms “captain” and “master”, captain is a title and a ship can in fact have more then one. Cruise ships have a “staff captain”. “Master” on the other hand is a legal term. A ship can only have one master.
If in fact a company appoints a properly licensed but otherwise unqualified person to be the legal master soley because the de facto master (anchor captain) lacks the proper license then likely they are in violation of the law.
The Coast Guard has investigated “paper captains” in the fishing fleet but it’s difficult to prove. I don’t know the details but likely only the most blatant violations were ever looked into.