Yes, it is, but I don't know how common starvation is for strays; I do know that it's not automatic and that America sends tons of perfectly good food to landfills every month. Sterilizing dogs and releasing them gives them a fighting chance that a needle does not (and that's not necessarily the form that euthanasia takes; amongst those other articles was one about a CO dog facing a gas chamber for a "repeated" attack against a human, even though it appears the first attack was by a different dog from the same household). They still have the chance to be adopted by a loving family; they just get more than a week (sometimes more, sometimes less) to find one, and even if they never do they still have a shot at a full life on their own.