well e and j are meant to be lolis but since all chars need to be 18+ to avoid legal problems both are same age as d. some will say that girls develop at different times (some can have c- or d-cup at 12-13 while some will be a-cup until 18th birthday or whole life or until pregnancy).
Precisely. You only have to look at the adult film industry, not just now but since it's inception. Fashions and tastes for particular body types change and dictate who the most popular female performers are but there has always been room for petite women. Take Riley Reid, for example. She has been one of the most popular stars for ages and is closer to thirty than twenty now but she has that petite frame and could still easily play a much younger role.
My personal favourite, Scarlett Sage, is 23 but frequently plays younger and has very small boobs and that same petite frame. Others like Sadie Pop (who is 25) are almost completely flat-chested and tiny. If she didn't have tattoos it would be all too easy to think she was underage. Compare those women to Traci Lords who gained notoriety for making porn when she
was underage but had a fully developed figure including 34d boobs (according to celeb facts).
Bottom line is you can't tell just by looking.