This is a somewhat advanced technique that I’ve been practicing recently. The idea is when you have multiple targets stacked or aligned very closely together, the transition is so minimal that your split times should be consistent across all shots, even during transitions.
You’ll find that most Master or Grandmaster shooters do this often and sometimes with targets that are placed further apart. The benefit is minimal compared to efficiency in movement and stage breakdown but at the higher levels where these shooters participate at, can make the difference between 1st and 2nd place.
I cobbled a video of a successful run I had this past weekend to demonstrate the effect.