This is a genre called mpreg, where men can actually get pregnant even without the omega or alpha syndrome.
Not really normal for men to give birth here, that's why Ci Nian is considered to be a monster by his father and himself. But I think Intersex isn't it as well because Cheng would notice two holes (where he has an operating vagina and womb).
For OP: I believe it is more of a convenient premise where the MC has a womb connected to his rectum which enables him to be impregnated thru anal. (unless this is possible in intersex where a womb is connected to the rectum, then yeah, maybe it is intersex related but I highly doubt it)
Yeah, yaoi magic it is, then, I guess
Yep, trust the magic of yaoi(▰˘◡˘▰)
I'm at chapter 9 and I'm so confused about the baby, where the heck did he come from? Is that what they meant by neither a man nor a woman? Hes actually intersex? But intersex people can't have two sets of working genitals, plus that would mean that his womb is in his ass, which make me very worried for his health