In order to make the break light visibly stand out from the light bar that goes across the back of the car, they turn off two sections of the bar on the left and right of the centre, leaving a portion of the light bar lighted in the centre.

Normally car manufacturers treat the light bar as a running light, and they add a seperate ‘third’ brakelight. Clearly at Tesla they didn’t want to alter the design, and this weird solution fits the wording of the government mandate. It doesn’t fit the spirit, but they got away with it.