...The bike may be fooling you. It can make one filament look like two by using two different voltage levels for tail light vs brake light...
...Canbus has a neat feature: When one filament is burnt out, it gets the remaining one to do double duty, as both marker and brake, by varying the power feded to the remaining filament.
Replace your bulb, and the Lampr will go away...
...The CAN-BUS system. This intelligent wiring system runs the bulb at a low 5 volts of power, enough to make it glow as a tail light. When you apply the brake, CAN-BUS bumps up the voltage which brightens the bulbs...