When position lights are on, they must not flash on and off ... they must remain on and be visible throughout certain angles ... NOW, LED brightness is a function of cycles per second, not neccesarily voltage change. Some LED position lights have a function that "dims" them for an instant, which to the human eye is "flashing". You see, they are never "off" during the perceived flash, therefore legal. They technically are not flashing, just ranging in intensity.
They are STC'd as original replacement with a simple placard on how to initiate the fake flash vs the steady light.