Gen 5 AWD mpg question

Considering a new Gen 5 AWD prius. I see that the LE AWD gets slightly better fuel economy (54 combined) than the XLE, Limited or Nightshade AWD models (49 combined).

Anyone know what the mechanical differences are that account for this?

The only other thing I see is that the LE AWD has tires that are supposedly (according to the online tire size calculators) one-half inch smaller in diameter. They are the same width.

They also show it as being .4" lower on ground clearance, which could be due to the tires alone, though those numbers don't perfectly line up. Turning radius is also a hair tighter...again, could be tires.

So - anyone know?