You have to read this thoroughly. They aren't saying water isn't part of hydration. They are saying water can't prevent dehydration. Dehydration is a condition where the body can not retain the water needed for a healthy being. Dehydration is when the body will not, for many conditions/reasons stay hydrated. I think they are stopping the use of the claim that water can prevent dehydration. Water is part of our hydration. Water can help/keep you hydrated. All they need to say on the bottle is water can help hydration
It's really semantics.

Or is it?
Our blood has an isotonic balance. Water is part of that and if denied water our isotonic balance will become unhealthy. So if my isotonic balance went off because of a condition not related to the amount of water intake then water would not prevent dehydration.
Think of it this way. You can get a stomach virus and you can't keep anything down. You've gotten rid of all food or water through the waste gate.

You've become dehydrated. You've consumed water as prescribed by all advertisers.You go to the hospital. The doctor doesn't give you a bottle of water.....He give's you chicken, stake n taters and beer in an IV
I totally agree about the tomato sauce not being a vegetable. Every one knows a tomato is a fruit! :BLAA:
Tissue hydration - Wikipedia, the free encyclopedia
Animals maintain adequate tissue hydration by means of (1) an outer skin, shell, or cuticle; (2) a fluid-filled coelom cavity; and (3) a circulatory system.
In humans, a significant drop in tissue hydration can lead to the medical condition of dehydration. This may result from loss of water itself, loss of electrolytes, or a loss of blood plasma.
Some invertebrates are able to survive extreme desiccation of their tissues by entering a state of cryptobiosis.
:Flash:
Still I think they should make the law makers sit with out any water for a while till they explain themselves properly.