I could be wrong there but I thought gypsum or CaCl would lower pH in a sparge just like it would in a mash. For a few reasons I don't really need to worry about my batch sparge pH so I've never looked into it to far. Acid I know for sure will help if you need to neutralize bicarb in your sparge water.
eta: if I am wrong on salts adjust pH in the sparge I'm wondering why so many brewing water tools suggest putting anything in the sparge beyond acid.
Nope, the salts added to sparging water do little to alter that water's alkalinity or pH. You can read about the reasons in the article "WHY Ca and Mg ARE NOT A SUBSTITUTE FOR ACID IN SPARGING WATER" that is on the Bru'n Water page on Facebook. The end message: Acidify your sparging water!
We add salts to the sparging water as a convenient way of maintaining the ionic content of the overall water additions. You can also add those minerals directly to the kettle if you prefer, but I feel that adding some ionic content to the sparging water might help reduce the tendency to extract tannins and silicates from the mash...but that is unproven.