Sort of related: this will work on Atlas trackers. For Darts it doesn’t do much (think shotgun; one extra dart in the shot doesn’t let you tag more than one enemy). For grenades, you get two that come out, so at some distance (where the grenades have had time to drift apart a little), you get a little more area. For pucks, you get two that come out that act independently of each other.
For the uninitiated, the pucks will seek out other enemies if there is still time left before they expire when their target is killed (within a certain distance of the kill). With two pucks active and a decent duration, this can effectively double the number of tagged enemies (especially where the population density is high with plenty of opportunities to spread). Even better: you sort of don’t have to pay attention or keep track to take advantage of this because the smart bullets take care of that automatically: just watch the barrel of the weapon for the ‘flare’ that indicates that something is actively tagged.