> From the sheer amount of different descriptions of this Aphantasia it should be obvious that most of it will cluster not in "disorder of the brain" or some such, but in "different levels of ability, due to skill".

Yes, though it was a shock to learn of its existence in my 30s, but probably explains why getting into drawing has always felt so hard for me, especially as I've never used reference images. I guess it's perfectly fine not to be good at everything, and it's never impacted me in any way in my life.