In my experience the people who most doubt aphantasia tends to be people who clearly have aphantasia.

I have aphantasia, but I have also during meditation had one experience where I could clearly see an imagined scene vividly, and the experience was nothing like when I "imagine" things and can't see them.

I know I wasn't sleeping because I was aware of the sounds in the room I was in for the duration.

But I also see images when I dream, but that one experience was far more vivid than any dream I've had.