Video demonstration: https://streamable.com/s/xlx02/jpmlp

Explanation:
A new item, a Salt Cluster in this case, is created every second or so, when the fluid count goes down, in the case of the CraftTweaker added recipe. The Vanilla Ironberry Juice to Tiny Piles of Iron Dust only poops out around 2 items per bucket. The GitHub Wiki provides no indication of one being able to edit this.

And when the water runs out, the items are kept being created at the same rate, until the Drying Basin is broken.

CraftTweaker script only includes this line:
mods.rustic.EvaporatingBasin.addRecipe(salt, liquid:water);

Drying Basin https://github.com/the-realest-stu/Rustic/wiki/CraftTweaker-Support#drying-basin

Well, I'm an idiot. Thanks for helping out.