That is carefully crafted language to keep NTSB investigators and Board members immune from being dragged into endless tort litigation.
No, it is the central tenet of almost all transportation safety boards around the world. It's also a major reason of why the NTSB was separated from the FAA (which does assign fault).
Besides, all US federal employees -- including NTSB investigators and board members -- already have "absolute immunity" against all torts when acting within the scope of their duties, except for violations of the Constitution or federal law (in which case they have qualified immunity, which may still protect them from litigation).