It's basically less of a "vagina" and more of an open, unhealed wound that these guys are putting their dicks into.
The post ops even have to stick stuff in their on a regular basis to keep it from healing up and closing.
This doesn't make sense scientifically. At some point they must heal, or they be running puss and develop secondary infections. Logically, they'd get a ring or something inserted till healed, forming a canal (dry hole), obviously not a deep as a normal cat. Then, get a life-time supply of lube. You can't pack a bed ridden patient for eternity without additional sores , so you definitely can't kept wet packing between gizel's legs.