I think it unfair to cast any blame on the jump-seater since we do not know at this stage in what capacity he was acting (I may have missed it!!). If he was 'safety pilot' then yes, he obviously failed. For all we know he could have been just using the j/seat to get to AMS.
Huh? Whenever I have a jumper, standard briefing is "speak up if you see anything". I remember as a university intern at an unnamed charter airline I was up front going into Rio and noticed the crew didn't descend to 10,000 as instructed. I was only 19, but sure as heck didn't sit there and watch things unfold!