Sweetie, everything about depicting sexual stuff is a form of fetishistic representation more or less. In fact, there's a breeding kink for women as well. Be it regular ass hetero porn, two guys just fucking or a pregnant dude who has lube leaking outta his ass, it all can be, and it all is a form of fetishizing. The point is that only the idiots reduce the sexuality and experience of these groups of people to a certain trope or representation.
Do you seriously think most of readers who enjoy mpreg go 'yeah. That's the gay experience. There's only a binary, and it's only valid when a twink dude gets pregnant by a hunky alpha'. Of course not, that would be ridiculous. Mpreg is mpreg. It's not supposed to be any representation, it's fiction depicting a fetish you either have or don't have.

we dont want to see pregnant men