It’s not for efficiency, it’s for longer duration flight with distributed electric power. I find that people look at aircraft like the Joby or Archer and get wrapped around the axle about limited battery duration, not to mention weight.
But they miss the advantages of distributed power. If the Joby had, say, a three-hour range it would be quite a capable aircraft. VTOL and faster than a conventional helicopter. Now they have find that sweet spot between weight, payload and capability. Might be doable.