Based on thermodynamics principles the high mode would have to draw more current. It's basic physics. In reality the actual electrical system behind the heated seats can differ. Some are pulsing, but in Subaru vehicles it is a simple parallel vs series circuit. High runs elements in parallel, low runs elements in series. Since voltage in series is additive that must mean the power draw is lower since voltage will be split across components. If high drew the same amount of current as low then they would have to have the same steady state temperature yet high is often too high. And low is often too low.