In theory, nDed, you are completely correct?
But here's the thing...
How does one get to the point where they figure out that their thing is male superheroes transformed into heavily-pregnant teenage girls? This is a very very very specific kind of fetish, especially considering that such a thing is not possible on three or four levels.
A pregnancy fetish? Not my personal thing but... okay... it's relatively common and there are definitely a lot of pregnant ladies running around. If there weren't there wouldn't be people for a whole lot longer.
A fetish for a "magical" sex change that actually allows you to make babies on the other side of the fence as opposed to just filleting your weiner, turning it inside out and getting a tit job? Again, kinda out there, but there are men and ladies all over the place, the fetishizing of crossing one of the few true "binaries" of human life that cannot be crossed makes some sense. Ultimate and complete identity transgression.
A fetish for fit women in skintight clothes energetically fighting crime? Hell, not only is it understandable, but I can basically get behind that one. Not to the point of making it a fetish but hot ladies jumping around in tight clothes is definitely nice.
A fetish for wanting to be older or younger? It's a common desire to wanna be younger when you're old or older when you're young, of course sick fucks are going to take it to the extreme.
Any one of the component parts are basically understandable.
But...
Could this dude (I have to assume it's a dude) have just woken up one day and said:
"Hey, you know what makes me wanna masturbate? Captain America turned into a sixteen year old girl, supremely cartoonishly heavy with child. Oh crap... I'm standing behind a couch... Ray is gonna be so pissed... UNNNNNNNNGH!"
I can see the pieces, I can see the picture...
I can't see how the pieces can possibly fit together to make that picture.
It is fascinating.