Thanks for the update. For years I use this with Ctrl, never got a thought to try without.
Btw, on the wiki page I mentioned is also written that: Under graphical environments (such as GNOME or KDE) 'Alt'+'PrintScrn/SysRq'+key combination generally only leads to a screenshot being dumped. To avoid this Print Screen feature the magic SysRq combination should include the Ctrl, becoming 'Ctrl'+'Alt'+'SysRq'+key.
So I guess it depends from the environment.