I do think variances in reporting are some of it. I have some visualization skills and wouldn't claim to be "aphantasic", but on the flip side, there is an enormous dividing line between real-world images and these imagined images. While awake I would never confuse the two.

I also suspect a lot of people are massively overreporting the quality of their images. It's very easy to imagine something and think you understand it, until asked to produce something based on it. This isn't just limited to mental images, it's the source of the "why don't you 'just'..." questions, and comes up all the time in building, engineering, artistic endeavors, etc. Your brain is easily convinced it has a thought with more detail than it actually has. I really only trust people who have taken a lot of time to train the relevant system if they claim they have these things. For instance, I really can design some somewhat non-trivial programs in my head... but I've been doing this for ~25 years, and only recently would I say I'm getting to the point where these designs are sometimes good enough that they're not taking serious body blows betwixt conceptualization and realization.

Yeah, I have asked people “ can you visualize Obama’s face on this piece of paper?” They say “oh, yes-perfectly! -it’s like I’m looking at a photograph” “Could you trace it and come away with a drawing that would compare well with a traced photo?” They can’t, and I think they are over-reporting the fidelity of their visualizations.

I can't play the piano, but I can mentally play back Flight of the Bumblebee in my head. The skill to produce and the skill to recall are different.

You could (or at least I could with little musical training) fumble around finding the right notes, and with enough time, eventually transcribe the song to sheet music though. mostly accurately.

just because you have no skill in shading and drawing lines doesnt mean that you shouldn't be able to replicate the correct proportions and details in the features of someones face.

Well, the image moves when you try to trace it, because your eyes are jumping around. Then, when you've got a wrong line, your brain tries to fit the imagined image to the wrong line by skewing it, which it does in several different ways once you've got enough wrong lines, so the wrong lines multiply.

A skilled artist can work around this, by drawing the right lines (and erasing / ignoring the wrong lines).

I agree that some people might under/over-estimate their abilities.

However, I am not sure if drawing is the right way to test it. I can visualise a straight line or a perfect circle, but I wouldn't be able to draw them perfectly.

Visualization is a bit confusing in the sense that I can perfectly "see" someone's image in my mind or on the piece of paper, but I cannot draw it that well. It is like a "floating image"? that gives me the person's face in my head, but I if I sit down and try to describe it with minor details or draw it, I cannot.

I couldn't do that if my eyes were open and Obama was in the room.

Yes, this. I honestly don't know if I see things vividly or not well at all because there is no baseline for comparison, such as a traditional vision and color test.

What's more convincing to me than self report of image quality is self report of imagery use. Whether it should be described as aphantasia I don't know, but I never think in a visuospatial way unless I consciously stop and try because the problem really requires it (and even then I feel I'm pretty bad). On the other hand I have friends that describe their ideas in such a visual way almost instantly, and report having imagery pop into their heads naturally.

To me it seems really obvious that relative to my internal monologue, my imagery is much weaker and quantifiably less frequent. So I think at least people that report having imagery much stronger than internal monologue likely have something different going on for real, not just with reporting.

I'm pretty sure it's just in how people report it. I was always quite good at geometry puzzles because I could picture the shapes moving in my head. Does that mean I can see images in my mind or not? It's nothing like seeing with my eyes, but I can definitely "see" it in my mind.

I suspect that people that play chess without looking at a board must have a somewhat clear picture of the pieces in their mind.