That behavior crosses species, up to and including the human race. It's just that a hummingbird is cute and we hate to see it.
Hopefully he was just cold and wet. I used to have birds and they would get that way when they overdid their baths. Then they would puff up and sit, preserving energy.
The only species that I have seen "fluff-up" is feathered species.
His behaviour was certainly not from over-bathing.