alt Hacker NewsI think I've read the article differently to you. It does not say that the afterimage is a test. In fact it calls it an illusion.
> This afterimage illusion, while a product of perception, serves as a bridge to understanding visualization
The way that illusion works is simple. You expose your eye to green light without moving your gaze (stare at the dot). The green receptors in your eye become tired in the receptor pattern of the apple. Then, you switch to the white light which is broad spectrum. You fail to see the green, leaving red (blue is almost green, and our colour triangle is not equilateral). So, you see an afterimage of the apple but in red. This fades quickly as your green receptors recover from the overload. It has nothing to with aphantasia and the article does not claim it does.
In a sense I agree with you that this is the intent of the article. I find this kind of laughable because I do not consider myself to have aphantasia (I can visualize things just fine) but the afterimage test is not even vaguely representative of how I visualize things.
But you can see people on this very thread claiming that they in fact do perceive visualization that way, and can overlay it on their physical vision. So you, in the sense of the poll at https://news.ycombinator.com/item?id=49469365, might be "No, but I don't have aphantasia", which is where I am as well.