OK, the entry in /etc/bootmenu.d didn't get deleted when purging the current version. I guess the filename has changed and the old one isn't incuded in the package anymore therefore package management doesn't know of this file anymore. I deleted the entry manually, rebooted and the 'naked' bootmenu appeared.

Now I'm curious: why don't I see those menu entries when backup menu is installed? There is an entry for powering down the device which I find quite useful. In backupmenu I can only see restart option (at least 'til 0.32).