For example, I can put an engine into a car, and still tell you where every part of that engine is located relative to every other part, without being able to see it, including the internals, and describe, for example, over the phone how to troubleshoot it without being able to see it at all in person - just a mental model. And, for reference, I have almost no fundamental knowledge or experience with engines besides taking one or two apart - and it would not extend to other engines. It's been at least 20 years and I could still do it verbatim.
I'm way out on the end of that bell curve, but I'm not unique. I've worked with people who found that ability completely baffling, and would have to break out diagrams and blueprints to do that.
The gap is a lot wider than you think it is, it's not subtle, and this is known as the typical mind fallacy.
Edit: And funnily enough, further down there's a comment about Feynman realizing that his friend counts visually and he counts verbally - and I'm on the verbal side on that one, unless it gets complicated, and then I end up tallying mentally - but I have to count them verbally at the end.
There was a couple who streamed on youtube who reacted to meme compilations, and years ago one of the things they reacted to referenced a similar topic. During that stream everyone learned the woman has no inner voice (including herself, she'd never even thought about it before and had no idea an inner voice was a thing).
While he was asking her what it was like, he brought up the voiceovers in tv and movies that were supposed to represent a character's thoughts. She had no idea that's what it was supposed to be, and always just thought it was some nebulous narrator describing what was going on.
I think any such signals would be a similar "wrong mental model" situation where you can usually only tell by poking at it with very specific questions or actions.
When I was a kid, I could visualize things so vividly, I could almost overlay the visual signal onto my real visual field.
The visual cortex signal was "loud" enough that I could trick the propioceptive parts of my brain.
E.g. I could visualize falling so vividly that I would actually feel the stomach drop sensation.
As I get older, I still have a very visual mind, but not nearly what I used to have as a kid. It also feels more "far away" from my actual visual field.
Though some days if I'm stressed, I don't seem to have as much control/access to the visual side of things.
So I kinda get where aphantashisa people come from.
I have wondered if painters and interior decorators and such were typically blessed with much better tooling for that.
I don‘t know how closely visual recall and creative visualization are related, though.
Not to say someone with poor visual recall can't make great art, it just may be tougher to make something closely representative from memory.
https://calteches.library.caltech.edu/3591/1/Feynman.pdf
worth a read, to me it kinda indicates that different abilities can be enabled by differences in how to mentally represent something. but yeah its debatable how much of difference in ability comes from/with a difference in experience but I my gut feeling is a lot more than you'd think. feels really hard to prove it as we only know what it's like to be us.
Either way, you've established a difference in subjective phenomenology and there are people on either side of that divide.
As examples I don't listen to music that frequently, I just listen in my head. I can hear songs pretty much completely in my imagination. I'll forget lyrics consciously but letting it play and zoning out the proper music and words appear at the right time. I can also watch days of kindergarten(or any grade) like it's video.
If people are trying to do that and can't tell a single visual detail from a memory or hum a passage from a tune I don't think it's a communication problem, there's just a real difference in experience. To be clear from my personal experience not being able forget stuff or not picture stuff you dont want to sucks. And I have some pretty bad tunes upstairs.
It's funny, I've never met anyone but my family who can do this like I can, so cheers! I always say I don't have a perfect memory, but I don't know anyone I can test myself against except my mother, who can "relive a trail ride she took 45 years ago down to the plants and opening and closing the gates". Having to remind people about significant shared life events is a real downer.