Yeah well the huge difference there is the fish is actually born with tissue of both organs, and once the change is initiated by hormones the ovaries that the female tissue was there for the entire time are made functional. They don't go to the doctor and get the shit cut off..

It is interesting however because it's all social. First you have smaller "females" that the male courts.. and a dominating female... That runs the show. And a male that was the biggest male... Once the largest female dies.. then the largest male activates it's female tissues.. and the next largest male whom has now become the largest male then starts courting the smaller females.

Real trippy, but the lesson is even in these cases it's scientific and the animal is born with the female tissue.

Other animals are born with both fully developed sexual organs rather than just the tissue of a female. And so they also just switch sides with organs or tissue they were born with.

None of them change sexes to a sex they didn't have the tissue for at birth.