Actually it is considered an extraordinary measure - prolonging life through artificial assistance.
Food is artificial assistance? What about feeding a baby with a bottle. Is the bottle artificial assistance?
Explain the difference between feeding Terri with a tube and a baby with a bottle?
Providing food and water through tube became an artificial means of prolonging life only in 1998 years after Terri collapsed, and you cannot presume retroactively that her wishes at the time were to be starved to death since that right did not exist at the time of her supposed statements to MS.