Even in the first century, about half the Jews lived outside Judea and it went down from there. And it's not like they were displaced by moslems. They just left.
I see why you would analyze it that way but I also see that it deserves a term in its own rights. As you said, it's all terminology. There are no objective definitions, at least not in linguistics
I've looked it up and lunar calendars tend to have 29-30 days months. Where does 28 days come from?