I agree that utility planners have their work cut out to plan for data centers. It's a different paradigm than what they're used to. I think they are being caught off-guard, but it's a matter of process and infrastructure. They typically plan around averaged or linear trends, but data centers can have volatile usage spikes, and supply can depend on e.g. seasonal rainfall which is challenging to predict.
Households with yards will have far more volatile water usage spikes related to seasonal rainfalls than a fully built out datacenter will.
A recent datacenter proposal near me was going to be built on a ~35 acre site. The entire site projected to use ~300 gallons of water a day when fully operational. That's including toilets, irrigation, etc. A household on a quarter acre lot in that area often uses 10-15,000 gallons of water in a month. 35 acres cut into quarter-acre-ish lots means a bit under 140 households. We'll cut it down and say 100 after streets and what not. That lot being a neighborhood like the others nearby would probably use at least a million gallons of water in a month, about 33,300+ gallons a day.