I would think that photo evidence would trump the sensors. The winner is supposed to be whoever first crosses the line, not the sensor. The athlete can't be expected to know exactly where the sensor is so that he can put his hand at just that height to trigger it.
I don't think such evidence exists, as apparently photo-finish cameras aren't used in snowboarding. But the sensors are at the line, so it's hard to see what difference that could make. Probably the Korean simply stretched forward better as it often happens in a tight finish.