When talking about how wireless power transfer is done, the standards (e.g Qi) distinguish between inductive and resonant mode. (Link)
They claim that when the units are in very close proximity it is more efficient to oscillate at the inductive side of the resonance frequency, but when further apart it is better to ride on top of the resonance peak.
Im not quite sure as why this is the case.
I know that oscillating on the inductive side have some pros, like ZVS to increase efficiency in the switching, but they also claim higher power output by using this at close proximity. why is this not the case when the units move further away from each other?