If you are going on a multi day backpacking trip in the desert you are going to be consuming a lot more water than sitting at your computer in an air conditioned office reading HN. And you also are going to need to be very cognisant of consuming adequate amounts of electrolytes (particularly magnesium and salt). You also would be wise to "camel up" at least a bit beforehand to make sure you are at peak hydration at the beginning (and of course anticipate carrying enough water with you or knowing potential water sources you can filter from).

People who are into running also become aware of this and those who do any activity in extremely cold and dry environments.

In addition most people have a base level of water loss (even while sleeping) through your skin that varies but is I believe around a half liter (specifically 400ml or 14 fl oz) per 24 hours. This is not the typical sweat out of your armpits from being a bit too hot - it's known as "insensible perspiration".

Water management is a very valuable skill and much more valuable than just trying to have some blanket "liters per day" recommendation. And getting water from your food is never a bad idea either !

I think it is an interesting finding and it would be interesting to hear more about the implications from someone in the field.

I only broadly understand this is some kind of peeking behind the curtain of some process that was not fully understood before

Do yourself a favor, and start drinking a ton of water!

I never had a water bottle growing up. Was I just constantly dehydrated? Seems like it.