My eigengrau is not completely uniform: there are subtle variations in monochrome intensity. If I concentrate on the eigengrau, interesting patterns can appear. I have some indirect conscious control over the patterns. For example, if I concentrate and ask for a red spot to appear, usually some shade of dim red will appear forming some pattern, but I don't have control over the details. I lost this ability some number of years ago, then practiced until I got it back.
I can only do this in perfect darkness with a lot of concentration, and I need practice to maintain and improve the ability. I think it's like this article titled "Direct Control of the Visual Field", where you teach yourself to control the Eigengrau: <https://zenodo.org/record/1429102>
The article on Visual Snow shows an actively animated noise field, and I don't see any animation unless I'm really in the groove. The Visual Snow article also implies that it causes distress, and that sufferers seek medical treatment to make it go away. That doesn't apply to me. I have never used hallucinogens, I've never had a migraine, etc. I consider myself creative, so that might be correlated.