In this answer over here it is explained, that a "question" comes up with aerosol cans, based on a gemora which asks if spitting in the wind counts as winnowing.
Now, the spitting in the wind case makes sense. There is wind, and the wind causes liquid to be "strewn".
However, an aerosol can is normally used indoors, where no wind exists. Even if wind does exist, the answer seems to imply that the presence of wind is not a factor here.
Now, aerosol works in the following way. A compressed liquid is put into a canister; when the nozzle is pressed, the pressure from that compression forces the liquid up the pipe, into the nozzle; and then that tiny hole of a nozzle causes the contents inside to come out in a pressure stream. (Having little space causes more pressure.) Due to the lack of pressure outside of the can, the contents then spread out in a cone shape.
So why is spitting into the wind compared here? Notice the gemora doesn't talk about spitting on shabbos in general, just into the wind.