This just popped up on a mailing list I follow. New recommendation is to use REIB (reboot even if broken) rather than REISUB. I think skinny elephants was always wrong too.
https://wiki.archlinux.org/index.php/Talk:Keyboard_shortcuts#Standard_shortcuts/Kernel:_Deprecation_of_the_long-standing_“REISUB”_mnemonic
https://lore.kernel.org/linux-doc/20190903160840.56652-1-kilobyte@angband.pl/T/