Is his ass both connected to his uterus and his intestines or how does he poop lol

The abo logic HHHHHHHHH it cant intersect with real life

Don't think too much lol. Or imagine cloaca but human, and there's probably specific mucus to let the stool smoothly pass without sticking, and on top of that it's self-cleaning like vagina.

I think of it more like the esophagus being connected with your bronchial tubes in the trachea. The epiglotis separates the airway by folding downward when food passes by. Just instead of food. Think of fecal waste passing through to exit through the anus.

I saw an omegaverse that described the anatomy of ABO logic, I wanna share it but I honestly forgot what manga or manhwa it is

I described it in my comment above yours. :)

Do search research on cloacas

I meant there was a visual representation, just for additional info but I can't even share it cuz I forgot which manhwa or manga it's from

Ohh! I saw it once in one too. But I don't remember the name either.