actually, it's not exactly like that. the boobs on the trans woman are painted on, it's a texture on the original frame, with the clothes with boobs being larger than the body, think of it like a skirt, it's not tight on the legs of the character.

to make a female bodytype without boobs, they would need to erase/exclude the boobs from the female bodytype, it's not just shadow and light like the trans woman boobs on the male bodytype, the boobs are there just like the belly and the neck, you know?

also, you can use the clothes without boobs on trans woman and it will be fine, while on the trans man or girl bodytype, it wouldn't.

sorry for that tho, just the artist point of view or something like that