I have a form of this, but it is not 100%. I can kind of visualize stuff, but I can't "hold" onto the image for long, it fades after like 5-10 seconds. However, when I am very sleepy and laying in bed, or maybe relaxed from alcohol, I can sometimes have extremely detailed and vivid imagery that is persistent, almost to the point that I could sketch a picture from it.
This leads me to think other things from brain are interfering with this visualization system and only when the other things are reduced by sleep or relaxation does visualization mechanism work for me.
All of the things you said are true for me, as well--as if I wrote it myself--but I drew a different conclusion: I don't think I have any form of it. I think we are seeing things in our mind's eye, for sure. Is it totally in focus, detailed, etc? No. But it's there. It's an image. It has a color. I didn't memorize the color of sunsets, I can---see them? Imagine them?
I never made a distinction between them before, before these discussions made me really think about it.
I can only see vague parts of a whole, like my object-detector neural net layers are working, and I can visualize lower layers of the network, but not the top layer. Like I can't remember my own children's whole face, but I'd instantly recognize it if I see it.
It makes me wonder if people's 'visual memory' isn't some for of GAN, where people with good visual memory just have great generative networks with synthesize details which aren't there based on broad parameters.
Because when I'm lucid dreaming, or partly asleep, I can have these vivid experiences where I can see imagined objects with perfect clarity, stable detail, even color, something I'm not able to do when normally conscious. Like if I think of red lips, or a red apple right now, I don't really perceive the 'red' -- its abstract.
Perhaps the real issue is a 'visual cache' that expires too quickly. Like if your brain is using GAN-like techniques to synthesize imagery from learned network weights, maybe some people have a better working cache, and so it disappears less quickly -- is more persistent.
I tend to think abstractly and my mind often gets filled with a bazillion ideas when I'm trying to imagine things, so perhaps I'm experiencing a kind of 'cache thrashing' that I don't get when sedated.
This leads me to think other things from brain are interfering with this visualization system and only when the other things are reduced by sleep or relaxation does visualization mechanism work for me.