During college I went on a desert survival trip in that same area, Deer Creek specifically. We went a couple of days without water, not because it was being withheld, but simply because there wasn't any.
Reading the news report, it should have been obvious that this participant was in need of serious medical attention. If that wasn't the time to use the emergency water rations, then when?
Another factor I don't understand, the group had water at Deer Creek in the morning. Why did they not stay along the creek throughout the day? Perhaps the creekbed was dry in other areas? A specific destination that involved traveling cross-country?
And of course it's always interesting how circumstances that might be mildly uncomfortable for some people are fatal to others. Walking five-miles in the desert, even with no food or water, would not normally be a life-threatening situation. I worked in the desert for several years as an archaeologist, and it was not unusual to drink all of my water in the morning (before the bottled water got too hot), and continue to work/walk the rest of the day.
-Bob
Edited to add: There's a big difference between participating in an organized group activity and setting out on your own. In the guy had been on his own, it would have been entirely up to him to make it to the next water location. But when part of a group, there should be some responsibility on the guides to make sure the group functions as a group. Specifically, if someone is falling down repeatedly do to dehydration, how hard would it have been for three some of the better-off hikers to fetch some water?