I know people that work in hospice, and they say this is a big misconception (the article hints at it too). they patients don't die from lack of water, they don't want water because they are dying, and their body can't process it. In fact, as you kind of touched on at the start, giving them IV fluids can cause them to drown since their body can't process the water.
Death is pretty ugly thing, that comes for us all. I got to learn the fun way that in the state of Oregon, it is illegal to disable a pacemaker. Even when the person has a DNR, and it is really the only thing keeping them alive. The best the doctors can do is turn the pacemaker down as low as possible, and hope its not enough to keep the person artificially alive. Which seems kind of really weird, when its also the first and one of the only states that allows medically assisted suicide..