So how can one man fairly low down the knowledge tree be held responsible?
Though Pilot Forkner is not
singularly responsible, he is responsible. As a member of a certification team, he is required to produce written reports of the design compliance of his testing. That includes an understanding of what the design requirements are, and how they have [or have not] been complied with. As a part of that, he, or one of his team members, also had to sign a declaration that there were no unsafe features associated with what he had been involved in testing. (Not unlike an aircraft in service really - if you've just flown it, and you think there's a defect, you report it for the safety of the next pilots and passengers!). So if, in his capacity as a pilot declaring the design compliance has been demonstrated, he either does not notice a compliance failing, or conceals it, he should be held to account. Otherwise, how can the public have faith in the certification system?