Well, I can understand why. During WWII, about 600 billion rounds of rifle and pistol ammunition was produced around the world. About 60 million were killed, with only 18 million of those combat personnel. Simple math will give you an idea of how many bullets were fired to produce one casualty. I suspect about the same ratio when hunting with a full-auto anything. A good example are the YouTube videos showing a bunch of guys shooting pigs from a helicopter using full-auto AR15 type weapons. Their kill ratio from single fire was much better than when they used full-auto.
Now if you're just trying to scare the daylights out of the rats (no pun intended), you're probably safe in saying you did. But if you want to snipe for real kill to round ratio, then single rounds make a while lot more sense.
By the way, the FLEX is a bolt action, so no chance of full-auto there.