In Fist of Fury Bruce Lee delivers 9 punches in 2 seconds (the flurry of blows is a real thing), even a sword can strike 2 times per second - 6 seconds is a surprisingly long time.
Autopassing a mental saving throw simulates extreme discipline or similar. Storys about spies resisting torture or Conan overcoming psychic domination both fit. Its a boon but not magic
(NB I'm not a fan of autosuccess either, I'd prefer to be a bonus to save. Its also why I think spellcasting should be a skill instead of autosuccess)