This change was made in LE12: https://github.com/LibreELEC/LibreELEC.tv/pull/8161 and backported to LE11 in https://github.com/LibreELEC/LibreELEC.tv/pull/8180 before LE 11.0.4 was tagged/shipped.
According to the patch/change, using "Shutdown()" as the mapped button command should restore the previous behaviour.
Do I have to play with the Keymap Editor (ugh), or is there another (easier) way to fix this? Can I modify the file in post #2 to fix it?