The delta-v is not needed to get a big enough impact. The delta-v is needed to be able to maneuver into an intercept orbit. In case you don't know, for rockets

The delta-v is not needed to get a big enough impact. The delta-v is needed to be able to maneuver into an intercept orbit. In case you don't know, for rockets the fundamental limit of their fuel is expressed in delta-v. Your kill vehicle doesn't need much delta-V if you can launch it close enough to an intercept course. But if all warheads are launched in very different directions, and all your kill vehicles need to start from a central starship point, they can't all be launched 'close enough' to an intercept course.