> Instead of just thinking about bundling a number of methods together with a data structure, you can make sure that a single method within that bundle works the way you expected across a number of objects. You might even be using these ideas in your code, but don't even realize it.

I think this was GP's point. They complain that no-one explains why the category theory _jargon_ is useful. As you point out, the jargon is not needed in order to use the concept. Someone might even come up with the concept independently of the jargon.