Dehydration absolutely can kill you during a race. Ask most (if not all) race medics and/or first-aid volunteers and they'll tell you dehydration is by far the bigger issue at marathons.

You took that quote out of context. If you're an elite marathoner trying to run sub-3:00 pace, then I stand by my comment to get as much water as your stomach can handle. Hydration is the limiting factor.

And if you hadn't taken that quote out of context, you would have seen that I was recommending between 60-70 ounces of water from 1-2 hours before the race until race finish, which won't put you at risk for hyponatremia and is, in fact, in line with what the American College of Sports Medicine recommends.