From an EU briefing on textiles and the environment:

Cotton accounts for 24 % of global fibre production, according to Textile Exchange. It can be problematic because it can require huge quantities of land, water, fertilisers and pesticides and cannot easily be recycled into virgin fibre. However, the environmental impacts of organic cotton can be reduced drastically compared with conventional cotton, as it uses less water and pollutes less.

The huge quantities of land required should absolutely not be underestimated as a climate problem. If we're going to survive this we absolutely need to give land back to nature at a massive scale, and the easiest (humanely tolerable) way of achieving this is to produce the same goods at a much lesser surface area. Lab cotton could, hopefully, be efficiently grown in a high rise building with a minimal physical footprint.

To make the Galy cotton, a team collects samples from a plant and harvests its cells. The cells are grown in bioreactor or fermentation vessels in a cell culture process similar to beer brewing. The final product is dried and harvested, with minimized water, land and energy use, Galy says.

Maybe I just misread the sentence. But the full quote seems deliberately obtuse to me. They don’t explicitly say that they need less water than traditional farming.