It's one thing to express such a "presumptuous sentiment" re a person whose wishes have never been clearly expressed anywhere. It's a completely different thing to express them (as is alleged to have been done in this case) re a person who has gone to the trouble of executing a living will, and spelled out very different criteria.
However, I tend to think this story in its present form is a hoax, or a well-intentioned embellishment of a true story. Hospices don't like to get sued, nor do their insurers sit quietly by in situations like this. If there isn't a clear court order to withhold nourishment, and there is reasonable doubt as to the legal authority of the granddaughter in question to be making medical decisions for the patient, the hospice would stick the tube back in fast, and wait for a definitive decision from a court.
Sounds like the hospice pretty much did do that.
The article says that the hospice did start an IV when the outraged siblings arrived. The next day, while her siblings were arranging with hospice for transport to a medical center, the probate judge granted the granddaughter emergency guardianship and the transport was not allowed.