In looking at places to stay in southern Spain, several places offewr a room with a 'shared private bath'. This seems like an oxymoron to me. What is a shared private bath?
Shared private means that all or most of guests use the bathroom, but only one at a time. A shared bathroom would be like a college dorm or military barracks where many people are using it at the same time.
I'm thinking a shared private bath is shared with one other room, not with all rooms ( which is hardly "private". I have seen this arrangement at B& B's, as an alternative to ensuite bathroom. If the bathroom is shared by many rooms, it will generally say " bath on the floor" meaning the rooms on that floor share the bathroom.
Gary's explanation is correct. There can be two or three private baths on the same floor.
It could also mean a shared toilet only room which shall I say requires more "robust" plumbing with a private shower/bath as part of your room which requires, well, less "robust" plumbing. Really old construction plays into this one. Shared private bath could mean, goodness, who knows what! Think Lola is probably most on target here.