AFAIK, a "super-organism" composed of individual entities is defined as one where the long-term fitness interests of those individuals and their groups are completely and permanently aligned.
For example an ant colony is a super-organism. That’s why it makes sense for a soldier ant to die for her queen.
Then why isn't a human a super-organism? We are composed of many different types of bacteria after all.
Some of the "entities" aren't aligned always, like when a person is pregnant for example. I think also our (human) cells doesn't operate as semi-autonomous agents with independent nervous systems and agency, unlike a ant colony.