A variant of the first is the highly imaginative user who keeps coming up with new variations or expansions of their idea. It’s not malicious but it can be exhausting.

Especially if you try to address their core need but their imagination doesn’t extend quite far enough to see how your effort would help, because they love their ideas.

I would describe those as a variant of the second, not the first. Those imaginative users may be polite, but they’re not understanding. While not rude, they are their own brand of entitled and high maintenance (I like your description of “exhausting”). One major reason I put them in the second category instead of the first is that the result is the same from my side, i.e. I interact with them as little as a I can.

To the first kind, in contrast, I’m happy to answer any question, no matter how silly it may seem, because I can be confident they’ll trust my judgement, that they’ll learn from the interaction, and that the next one will be even better. Just about the only thing I’m sad about regarding those users is that as they grow they start interacting less because they don’t need it as much, as they are able to help themselves.

Now that I think about it, that seems like a good way to differentiate: The good users delight you and demand of you less and less; the bad users drain you and demand of you more and more.

I can imagine the kind of person you're describing, and I find the idea of the burn they get from reading this hilarious. They sound innocent and quirky.