If you just say unvaxxed, then people will ask about "partially vaxxed". If you put "partially vaxxed" in a column of its own and it shows even the slightest protection, you get people thinking that they can just get the first dose. If you put "partially vaxxed" in a column of its own and its show no protection similar to being unvaxxed, you get people saying, "see, the vaccine doesn't work".