Sounds more like a nerf to me than an actual usable augment.
Nades are supposed to be hit directly for massive damage or fired at a choke from a distance away.
Giving lock-on means you have to get closer to that choke and risking gunfire.
I however, think that nades should insta-explode enemies on hit regardless of distance. This will get us into the mindset of “Hey, that guy’s right here, and I have a grenade launcher. I should shoot him and deal 90!” instead of “Hey, that guy’s right here, my nades are gonna bounce off him, better switch to my primary in a hurry and hopefully not die!”.