You're technically correct, although there usually is some make-up that's periodically necessary. You'll want to blowdown some of that water from time to time to try and prevent scale/accumulation and even biomass buildup. It's probably on the order of like 1-2%, and probably not continuously.
It would be better for the article to quantify this amount of water, that's regularly leaving the system and needs to be replenished. 1% of 700,000 L is still a lot of water, but it's very hard to measure the sustainability impact without knowing how often they happens. Once a year? Multiple times a year? Or once every few years?
Just for my credentials, I'm a chemical engineer by training and I used to do a little work with a closed loop steam generation and cooling system.