I'm sure that's the closest description of what I observe. For me it works in this way: I'm bad at recalling past moments and if they form, they are vague vanishing grey photographs, but I can create and transform 3D models, all of that is done entirely in my head without any visual effects coming from eyes. Just like you I also have really good auditory memory, in fact I can sense Giant Steps playing at the moment and I'd say only the drums are hard to remember.

I'm not sure myself. Growing up, I remember being frustrated anytime I was asked to imagine something. I imagined what other people's imaginations were capable of, which seemed like so much more. Where reading a book would lead to a movie playing in your mind's eye.

But still, I can see a short column of numbers and add them, move the carry, etc. But it never seemed like the visualizers could.

In my experience, "a movie playing" wouldn't be the right description. I never have a super clear image of characters in my head. More like a vague cartoony idea that can morph drastically through-out the book or even when re-reading. Once I see a movie though, I'd have to force the imaginary version back. Without effort, it's probably the actor in my head, but still not super clear.

Environmental descriptions seem a littler clearer and consistent, both man-made stuff, like buildings and vehicles, and nature, but still nowhere near stable.

One thing I just realized is that, when it comes to audio, I can both imagine and recall far more clearly than anything visual. And, now that I think about it, it feels 100 times more clear.

Can you "hear" in your head?

I sometimes get portions of songs stuck in my head for a day or two, but otherwise no music unless I'm really tired. The depiction of hearing someone else's voice when reading a letter from them always fell flat with me.