Even the golf course trade association only claims 10% grey water use.

Also, you're going to be shocked, data centers can cool with grey water as well. The now-cancelled Project Blue data center near Tucson was going to build and operate a wastewater pipeline and treatment plant and give it to the city, but the shouting NIMBYs prevailed anyway. The developer now intends to use air-to-air cooling, which costs more energy.