Exactly. The demon’s hand is presumably limited to the speed of light, as is the position or state of the switch’s physical lever, &etc. After a certain point the lever will not be able to reach its fully “on” and “off” position before it must change direction. Eventually it must stop moving entirely. The stopping point is necessarily before 2 minutes have elapsed.
Assuming the demon is forward thinking enough to stop before reaching full-on so he has enough time to get back below the threshold, the stopping point will be when the lever is exactly halfway between on and off. The resultant state of the switch would depend on the specific switch, I think simpler switches would technically be “on”, due to arcing that could cause melting or even a fire. More expensive switches would have a dead zone in the middle which is handled by springs based on the previous state (eg: if off, you must lift it past 100 degrees to switch on & if on, you must push it down under 80 degrees before it switches off). Can’t remember the word for that.
~Max