Or the tendency to exaggerate to make it easier to sexualise. I mean it does make sense that anything disproportionate seems easier to sexualise, especially if it’s an erogenous zone. It’s like having huge muscles but small genitalia. Even if steroids aren’t involved, if you have huge muscles your penis doesn’t seem that large anyways. It gets dwarfed.
(The sort of thing some have been pointing out and should a study state that most black men aren’t well-endowed, even most black athletes actually have small genitalia then that’s still proving my point in some way.)
But in a weird way it seems more proportionate. A good number of smut, whenever it does sexualise buff men at all, don’t just give them huge muscles but also blow the genitalia out of proportion. It’s also very in-line with the supernormal stimulus as it involves exaggerated erogenous zones. If that’s the case, it makes sense really.