I've never seen that myself, but it's probably not that unusual. That mask is filtering out 0x2000 and 0x4000 (the Nunchuk buttons) as well as 0x80, 0x40 and 0x20 (three unused Wiimote button values, which are what I use to check for fake inputs that I've created, e.g. Wiimote shakes, etc.), so...