
Xl, xxl and even xxxl are straight sizes just like xs-l, they have sister plus sizes but its like bra sizing where a sister size is not an equivalent fit and most actual plus size people dont fit well even into the larger straight sizes listed and vice versa, midsize people on the higher end of straight sizes arent well fit in plus size clothes
The average size (in women atleast in the US) is 14-18 which is L/XL anyways so thats an odd straight size range to select; not to argue just to educate! In terms of the actual question posed I think the answer is different for small businesses, customs, etc vs major brands who can v easily fork that bill