Poorer members of the insurance pool have their premiums subsidized. From the insurance companies point of view, they are (theoretically) managing the pool and premiums using the same actuarial tools they used previously.
The rules about not being able to reject people for pre-existing conditions force them to broaden the set of (heterogeneous) members included.
The plans are provided by “health insurance companies.” The product you buy from them is called “health insurance.” The imaginary, purist notion of what you are declaring to be “insurance” is like a simplified model of economic theory you might find in a textbook. It’s used to gain insight about how an insurance product works. There are no real world example of “health insurance” that conform to your simplified definition.
Health insurance in the US has long included coverage for routine care, which already falls outside of your model.
I’m of the theory that the meaning of words is defined by how they are used in everyday language, not how I think they should be defined.