I'll wager it's the figure he's working on in his
WIP thread. Which means he's got the macro setting from...well...you get the point.
One thing it probably is - the primer. Think about how it's applied, tiny droplets sprayed through the air that land on the mini. Of course it's not going to be smooth or even, especially up close. What primer are you using?
This is a huge problem, no matter how good you are at priming, in the model horse hobby. The larger scale horses show this and add pigment and it becomes obvious. So we sock out the model.

It's a play on words. Sack out or sacking out a horse is a term used to "de-condition" the horse from it's flight response. It's frowned upon now because the horse can injure itself. But the idea of getting a horse accustomed to scary things is still very much used. Anyways, to sock out a model, after the primer has cured 24 hours, take two old cotton socks, turn them inside out and put them on your hands like sock puppets. Then you rub the model until it's completely smooth. This evens out your primer and if you're working in pigments stops grain issues.
For minis, it's more difficult because the sock can get caught on the fine detail. I get the larger areas with the socks, for medium areas or areas with raised detail I take the socks off my hands and take a tiny corner and rub lightly usually in one direction away from the snagging detail. The small areas I get with cotton swabs. Usually you can do this while chillin' out and watching TV or whatever. Except for the really tiny spots of course.
If your primer is going on gritty or furry it's probably due to heat/humidity or not shaking the can enough. But small uneven areas like your picture is simply the nature of the beast when working with an aerosol. Can't change physics unfortunately. But the socking out the model will take care of it.