Thanks for your questions Jerevan!
I have not noticed any extra dust introduced by the flocking paper. The flocking paper is quite clean as it comes from the manufacturer. If it becomes dusty during installation on the enlarger, then it tends to trap and hold on to that dust. A so-called "lint roller" would be the most effective way to remove trapped dust. And finally, if the flocking paper becomes dusty after being installed on the enlarger, then you have a separate problem of dust entering the darkroom, and that is unrelated to the flocking paper itself, although as you have pointed out it will be more difficult to remove dust from the flocking paper compared to a painted surface. I have sealed off the forced-air heating vent in my darkroom in order to reduce one of the main sources of dust in a home darkroom.
Installing the flocking paper in my darkroom was a part of a group of changes that I made all at once, as a result of my participation in a John Wimberley printing workshop. Yes, my prints are much better after making these changes, but I also changed paper, print developer, stopped underdeveloping my prints and over-taxing my chemistry capacity, started controlling print time for developer temperature, upgraded my negative carrier to multicoated glass, began aligning my enlarger (every time I load a new negative in the carrier), switched to a dichroic head, and made the flocking changes discussed in this article.
So obviously, this is far too many changed variables to allow me to say with certainty that the flocking paper improves my prints. John Wimberley's prints, to me, are as close to perfection as I've seen. I think that part of that perfection comes from his attempts to optimize every part of the image quality chain. The idea to use flocking paper to reduce enlarging flare is his, and I believe it makes a positive difference in print quality, but I can't prove it.