No, fastball hurts some nades and buffs others and sometimes a playstyle demands that fastball be either on or off regardless of grenade. If it was intrinsic that would blow to no end. It either needs to be a toggle on the armor piece without requiring the mod (traction would get this too on boots) or it should be left as is. I think fastball is enough of a modifier on grenade usage and playstyle that it can stay as is. It being a mod that only costs 1 makes sense.