Depends:

How humid is it? How hot is it? Are you in the shade? What are you wearing? What are you doing? Are you otherwise healthy? Are you bleeding?

If it is between 65 and 70 degrees F with ~70% humidity and you aren't moving and are in the shade then your water consumption may be very little and you would have no ill effects. For example, I sit still in that environment every day of the week and drink large amounts of diuretic coffee and almost no water and seem to be none the worse for it. (A little jittery but that is probably due to the caffeine rather than dehydration).

OTOH if you are walking accross the desert at noon in august with shorts and T-shirt and the temp is 140 F and 0% humidity you should be drinking about a gallon / hour or more and you will need to have some salts on-hand to keep your electrolytes in balance.

There are scenarios for everything else between. The 1-2 liters per day is a rule of thumb for most of the moderate situations where you will be active but not unduely stressed.

The fellow in the story related at the start of this thread was in the shade in temperate environmentals with rain, couldn't move due to injuries so physical activities were low, didn't seem that he was bleeding much, had enough clothes that he didn't become badly hypothermic. His body was probably using what water he had very efficiently and not losing much.