If the transmitters continued to operate after battery exhaustion, then I may begin to question the laws of physics, as well as my life choices
They just have access to classified physics and definitions of energy most people don’t have.
Small solar panel and a charge controller. Defeat physics with this one trick.
It's weirdly phrased, but it just means that they don't have a tight control for battery capacity. Their device is designed to operate for at most ten hours (for example), but the battery that they use could have anywhere between 8-12 hours of supply, so the transmitter would be active anywhere between 8-10 hours.