#331 Kernel mistakenly creates joystick devices for pads
It appears that the joystick driver (at /drivers/input/joydev.c) is informed about the creation of most new input devices(1), and uses a filter function named "joydev_match" to try to exclude non-joystick devices. Unfortunately, this function does not appear to exclude pad devices since they do not meet any of its exception criteria. This does not cause significant issues, but is a source of confusion for some users. Fixing this issue will require either changing what kinds of devices are ignored by the joystick driver, or changing the events associated with pad devices to ensure the joystick driver ignores them.
1: Looks like anything with "ABS_X", "ABS_Z", "ABS_WHEEL", "ABS_THROTTLE", or anything with at least one button in the range "BTN_JOYSTICK" through "BTN_DEAD" (including "BTN_BASE"), or one button in the range "BTN_GAMEPAD" (including "BTN_A").
fwiw, joydev is regarded as deprecated, so I'm not sure any changes to it are worth investigating.
Linuxwacom has moved from Sourceforge to Github. If this is still an issue please reopen the bug there.