What is mid size, is it just a nice way of saying plus size?

What is mid size, is it just a nice way of saying plus size?

So I saw that dumb news on the phone and it was a bunch of titles I’m mid size and I did a clothing haul at target and nothing fit. Etc

To me there was nothing logically mid size about these women they were objectively obese, is this a new word for plus size or an American thing?

What is mid size, is it just a nice way of saying plus size?
Post Opinion