If there's no air, it can't collect water from the air, so there needs to be at least some atmospheric pressure, right? Optimally it should work slower on planets with lower atmospheric pressure... but I don't know anything about factorio modding so I don't know how possible that is.

It is a bit complicated to add a variable production depending on the planet properties, my original idea was similar, but giving the player the ability to produce water in every planet with an atmosphere could break some mods progression so i decided to go with the recipe approach, with time i will add more planets to water harvesting or any mod can add its own recipe :)

Oh, it has per-planet recipes? I didn't know that was a thing.

Yes! each recipe is balanced for each planet, and they are lock by surface conditions.