@dpiponi I haven't had ~any experience with wireless charging, but did experience something similar with wired charging: if charging keeps stopping and starting (and operates at low power when it actually does), a phone can easily lose more energy on all the state changes that happen in software than it gains from the charger.
That said, this happened to me only when charging a device that was on.
@robryk My AirPods really shouldn't be doing any work while "charging", they're not really "on" (whatever that means these days).