The NTSB Board members do not direct or control investigations, they do however control recommendations for avoiding a similar accident scenario.
They do respond to politics (they listen to congress and the president) They also listen to beefs from the industry and the public.
What's nice about having a PHD in an aviation subject, is that they can more easily understand and weigh proposed recommendations for corrective actions for a contributing cause.
Maybe it's just my cynicism but I would suspect that a HF guy would be more likely to blame the machine for putting undue pressure on the crew, while a technical guy would be more likey to blame the crew for not accomodating a seemingly benign system failure
but then there is that fleeting thought that we all just really want to prevent another similar accident rather than apportion blame
