I've heard of this happening before; a fever of about 100F causing improved executive functioning in autistic children, for example. It's one of the things being studied in autism, initial reports were 30-40% of autistic kids have improved executive functioning with a fever as well as seemed "less autistic".

In those cases, I've not seen studies of them figuring out why, just that it there are affects on pupil dilation, there is affects on how stuff travels in the brain during a fever, and it ends up with people looking more normal. They needed more studies and I've not seen those ones.

I'm not sure how common it is in SPD. It's hard to find SPD studies unless its specifically through the SPD Foundation. For SPD I try to piece together research from the SPD Foundation, stories of SPD people, and adding autism research in when I know of autism research that'd be relevant to the situation (because its frequently a place I'd start looking if I was doing SPD research).