I didn't notch the bulb or its base, I notched the bulb socket (the brass piece in which you insert the bulb). The stock bulb has two filaments and thus two positives on the base of the bulb. The negative connection is to the bulb brass outer shell.
Only one of the filaments lights on the US version of the KDX. (The other may be for a high beam switch that the KDX doesn't have and the socket isn't wired for). So Craig, yes, only one filament glows. When this filament burns out, flipping the bulb uses the other, still good, filament.
Adding another notch to your socket has one added benefit: If you run a bulb with two good filaments you are in effect carrying a spare since you can flip the bulb and be on your way.
Sorry about the confusion.