I don't know if you asked but he did it anyway
I personally suspect that it's mostly the difference in riders that made the difference in consumption here. Can be tested by swapping riders (and riding that route again). If not just the difference in wieght and height of riders it can also be in riding style. Even when they ride together maybe one is not as steady with the throttle or has regen set differently requiring more input.
The different gearing will result in different RPM for same speeds. I wouldn't expect that to result in a 10% difference though. If it is noticeable it'll likely be a lot less.