By my calculations, a 1/2 drop in my 16 x 36 pool only equates to approximately 150 gallons. I don't think my water softner will be overwhelmed. Even at twice that level of evaporation (which we can have here in the desert), 300 gallons per day extra water use wouldn't be a huge problem for the water softner.
Trying to fill a pool with softened water would be an entirely different matter.
I don't understand what you mean with a 1/2 drop in your pool with 150 gallons.
As for softener size and it being overwhelmed, it all depends on what it's capacity is, how hard the water is that you put through it, how much, and when how often it is set to re-gen.
What I am saying is that most home softeners cannot reasonably keep up with the demands that a pool needs, along with supplying the house. Yes, it is a bit different when it's dedicated to the pool, but this is a very unusual set up. Still, it becomes a question of practicality when you factor in salt use, brine effluent, and water use in general to get this all done. With very hard water, 300 gallons a day would create a need for pretty frequent re-gen.