I assume they are requesting those large breasts. I also assume those posters are teenage boys who have never touched a breast, let alone a massively over sized one.
Jessica Rabbit is hot I agree with that, ai will produce whatever you tell it to produce. If you're not impressed with what you're seeing that is a limitation of your own imagination. These models will always take some creative license but they're not actually producing anything, they are the medium With which you and I can produce.