Without any more information on frequencies and measurements it's impossible to know. My guess is either A) They did not perceive the dimming, and/or B) The fre

Without any more information on frequencies and measurements it's impossible to know. My guess is either A) They did not perceive the dimming, and/or B) The frequency was high enough that the inductive and capacitive effects of the circuitry became relevant and was filtering the PWM signal to DC signal that still drew the same amount of power as it did when fed the full voltage DC signal