had the definition been properly worded (ie, beyond reasonable...)
That is the 'properly worded' standard of proof when aircrew are still alive to give their account of what happened and defend themselves.
Aircrew who survive have all the rights and protections associated with a fair trial and also have the right to appeal against an adverse finding.
Aircrew who die have no such rights.
That is why a higher standard of proof is required before condemning aircrew who are dead and can't defend themselves.
“Only in cases in which there is absolutely no doubt whatsoever should deceased aircrew be found negligent”
bizarrely misworded burden of proof
seems very clear to me.