The pool does use a ton of water when it gets (re)filled, but that's only a few times a year. Filling the entire pool uses about the same amount of water as the average California golf course uses in one day...
It’s also just localism all over again, except now it’s just straight up money that keep you out of the club instead of a more abstract idea of being a local.
The Surf Ranch is a high-end/test pool, and they've been pretty open about that.
Source: Got to visit the wave pool and talk to the employees during the Surf Ranch Pro in September.
EDIT: Follow-up. For point of comparison, while 300,000 gallons sounds like a lot, a "storm" in LA can drop 100 million of gallons of rainwater in 24 hours...LA's catchbasin system absorbed 22 billion gallons of water in the 4 month period between October 2016 and Jan 2017 (https://www.scpr.org/news/2017/01/23/68360/how-much-storm-wa...)