User blog comment:HollowIchigo58/High School DxD Season 4 Announced/@comment-90.202.240.151-20161027033301/@comment-9595671-20161028033536

We're referring to the girls by their natural sizes though, since they can't make themselves bigger or smaller like Ophis can. And Ophis' natural size is kinda wonky to figure out due to her being a genderless being.

Actually, female devils can't change how they look, they can only chance how young they look. If they could change how they look then Katerea would have been able to infiltrate the summit between the three factions rather than teleport in.