This posting is older than 6 months and can contain outdated information.
Thanks for the additional info.
The Wii Remote only sends data for its "normal" buttons, but doesn't
send any data for the power button and the small, red reset button
located under the battery cover. Its press therefore can't be
detected. It appears to be tied in hardware to directly close the
Bluetooth connection and power off the remote's hardware.
Best regards,
Felix Schwarz