AI most definitely uses more water than a traditional full text search because it is much more computationally expensive.
The water figures are very overestimated, but the principle is true: using a super computer to do simple things uses more electricity, compute and therefore water than doing it in a traditional way.
I mean, think of it this way. If I built a web app that took HTTP requests and converted them into a YouTube video, then downloaded and decoded that video in software, and then served the request, you'd say "that's stupid - you're using 10,000x more compute than you need to".
It's a tool, and using the wrong tool for the wrong job is just wasteful. And, usually, overly complicated and frail. So it's only losses.
The water figures are very overestimated, but the principle is true: using a super computer to do simple things uses more electricity, compute and therefore water than doing it in a traditional way.