How did you determine you have aphantasia? I definitely feel as if I cannot visualize things the same way as others, if at all.
A big part of this, ironically, came from a discussion of Tears of the Kingdom, where my friend was simply unaware of the mechanisms he was using to solve the little visual puzzles. Once he started understanding how concepts like plane rotation mapped exactly to what that video game required, we both sort of had to pass on a belief in hard aphantasia. YMMV, totally possible that things like this are or at least seem impossible.
At any rate, I’m not sure the presence or absence of visual reasoning skills has much bearing on memory, as this particular guy has an incredible knack for learning languages that I just don’t have in the same degree. At any rate, all I want to do is encourage you in your quest for better memory skills!
On the other hand, I can see hypnagogic images directly before falling asleep. These have fidelity, color, detail, look real, and are definitely visual. I also lucid dream occasionally, and the amount of visual detail there is more than I see in real life because of bad eyesight.
The cube I'm "picturing" in front of me, though, has no visual component at all.
I also remember reading about how in some study they watched the brain activity of people with normal visualization capabilities where the visual components of the brain lit up when they were visualizing but did not light up for people with aphantasia when they were visualizing (or trying to).
If people really have no visual component at all when they picture a cube in front of them, then I would agree that aphantasia is not a thing. But people I talk to go on and on about the level of detail they see and what they use visualization for without even consciously thinking about it.
Quite because that is not how the brain works, when imagining something we merely instantiate a generic of that class, it has no visual component although it has attributes, some of which may convey a visualization - the cube is red, the cube if oriented in the cavalier elevation, you describe it yourself as being "in front of (you)" in what regard could you consider this to be true even if it were inside of your head?
Through language we have been convinced of something that simply is not true, nobody wilfully hallucinates (internally or otherwise), to be aphantasiac is not to be special but to be aware of one's consciousness in a way that most people seemingly are not.
Of course it is self-diagnosed, even a pathological rubber stamp relies entirely on self-reported symptoms.
Interrogate anyone on the subject of their visual imagination long enough and you'll eventually bump up against inconsistencies or otherwise reluctant admission that they don't "see" anything.