This, in my mind, is the ultimate issue here.  I'd like to believe that ACs across the fruited plain would never make a BS crew rest/flight safety call, but it happens (Texas Hold 'em?), so someone has to make an imperfect judgement call on whether an AC is making a legit call. 
  
It's hard to prove something didn't happen...did Capt America save the day by calling crew rest?  Impossible to know when/if you've broken the mishap chain.  We only get good evidence when we don't break the mishap chain and someone dies.  They'll second guess you either way.