I would have to disagree. I can agree that in the moment, during a firefight, it is the best perk. However, the reduction in flinch is not significant (33%). Additionally, if you are sniping correctly, you should be getting the first shot off. Specific to using a low magazine sniper with final round, surplus has better utility (E.g. ammo dumping). Surplus gives double ammo on every pickup. While special ammo isn't overly scarce at the moment, Bungie has already taken steps to reduce its availability. Further, it is probable that this trend will continue.