With respect, I couldn't disagree more.
I have indeed thought about the second part of the statement and have been arguing about the water consumption myth for some years. I've done so on MAB before.
For my money, it's one of the more pernicious bits of nonsense that has slipped - largely unchallenged - into the health industry. It began with the wonderfully named Dr. Batmanghelidj, who must have some sort of record for the number of people he has successfully made paranoid about something they have absolutely no need to think about.
Certainly, under some circumstances, it might be possible to outstrip the thirst trigger. It would be prudent to keep your fluid intake up, for example, if you're walking any distance in the heat or working construction. But for most people in temperate climates, who aren't being fantastically active, their usual drinking patterns are going to be plenty to satisfy their needs. I suggest that anyone who is worried keeps an eye on the colour of their urine. If it's orange or brown, maybe it's time to drink something. Other than that, stop worrying: thirst isn't like the oil light on your car (you know, by the time it's on, the damage is done).
There's absolutely no evidence that healthy people need to hit some sort of arbitrary target for water consumption. Homeostatic mechanisms are a physiological marvel, and cope incredibly well at conserving water. Someone in temperate climates stands more chance of overwhelming these by over
As a bit of weak-sauce anecdotal evidence, I sip water in the gym -because I sweat buckets - and on a work day, I drink 5-6 cups of tea/milk. That's it. I've never had any symptoms that I could reasonably attribute to dehydration.
P.S. It's another myth that tea and coffee dehydrate more than they dehydrate.
P.P.S. Just because the body is composed of 60% water - or whatever it is - doesn't mean that you need to think about topping it up more. By that logic, we would need to ensure we're breathing x number of times a day, as we're composed of 65% oxygen atoms (by mass).