Right, but it's not fair to say that it just outright boosts their paths, the OP was already struggling with this.
And I'm quite sure it doesn't apply to paths that they lack - I've had too many S1 Slaves fried to death by overzealous Masters topping off their script with Blade Wind or Gifts from Heaven spam (when the Masters' level is high enough, the Fatigue should be negligible, unless the slaves were not getting the same reduction).