Anecdotally, ADHD has nothing to do with this. Or rather, it has as much to do with aphantasia as aphantasia has to do with how prolific a reader someone is.

My ADHD used to make me constantly daydream and disappear mentally into incredibly vibrant internal worlds and it regularly impacted my ability to focus on schoolwork because I would draw flipbooks of what I was seeing.

I can sharply visualise autobiographical memories from when I was 6 months old of me crawling on the dining room floor and have had aunts and uncles confirm the shape and color of the chairs around the dining table on my left, the curling of the woodwork on the china cabinet to my right, the paisley pattern of the runner rug leading from the dining room to the den that I just crawled onto and can still feel the fibers on my knees. I left that house to never return when I was a year and a half old, and never saw pictures of it either.

On the other hand, I also have dissociative amnesia from everything that happened after that 1.5 year mark, so a lot of 5-10 is a huge bubbling black cauldron that occasionally burps out an autobiographical memory of some traumatic shit, or some mundane memory tangentially connected to something traumatic.

This to say, I would be more willing to accept a connection between aphantasia and SDAM, since you can't, with the same fidelity, reencode memories you can't visually recall, than I would be to accept that ADHD has anything to do with aphantasia at all, from my position on the other end of the mental visualization/autobiographical recall spectrum.