In my experience isolated DC system or isolated ground DC system. But still pays to make sure whoever one is talking to though has the same understanding as to what you are referring to as the terms are used loosely. In a good alluminium ship yard they will know immediately what you are referring to, elsewhere others may place their own interpretations on the terms - like your comment about ending up in endless discussions.
My own boat
is so fitted - I just made sure that the yard that built my boat
had a very good systems engineer
who understood that isolated means isolated and also understood what was required to achieve it.