As a hypothesis at least it seems probable, just based on lift disk size and proximity. Lift disks closer together form more of an annular lift ring around the craft, for more uniform flow, and larger disk areas in general should lead to increased hovering efficiency.

In my experience flying octa vs quad, the octa definitely outperforms the quad. This was some time ago and DJI has made improvements in leaps and bounds to something like 30mins for a Mavic now? But back then, the octa easily had longer flights as it had larger capacity which was filled by larger batteries. It was also easier to fly/handle. Essentially, I'm just repeating/agreeing with everything they said on pages 11&12.

this has been my experience, too.

more rotors = more power consumption capability, but in practice it yields lower duty cycles for each of the motors. That effect, along with additional lift capacity for batteries, creates a platform that generally stays up longer.

as others mentioned there are also aerodynamic advantages as long as we're staying away from coaxial designs.