“Could”. More likely it was closed loop. As I understand it this is an estimate, thus the word “could”. This has nothing to do with using closed or open look water cooling. Water isn’t single use, so even if true how does this big number matter.
The point they are trying to make is that fresh water is not a limitless resource and increasing usage has various impacts, for example on market prices.
The outdated network holding back housing is that it doesn’t go to the right places with the capacity needed for the houses. Not that OpenAIUK is consuming so much that there’s no power left. To use a simily, there’s plenty of water but the pipes aren’t in place.
The point being made is that resources are allocated to increase network capacity for hyped tech and not for current, more pressing needs.