From comment just above:
"... An accident ... flogged to no end ... let MI185 be inconclusive...."
There is more to this than just the NTSC's MI185 _investigation_: in the mid'1990's the USA's NTSB committed a few major errs (though COS, PIT, and 800 cases were _investigated_ to a proper conclusion).
The USA's NTSB still holds an undeserved reputation as a good investigating authority. I liked that TV-show's (above) interview with Feith -- Feith (former NTSB) clearly expressed Boeing's absolute certainty about the SilkAir INITIAL upset.
So, there are some good reasons why the NTSB's staff should be suspect, some errs (biased-botched investigations) that need correction. USA-law lacks any means for reviewing NTSB-staff errs, NTSB refuse to comply with their own rules for "reconsideration"; & the 9th Circuit Court decision stated the NTSB enjoys "unreviewable discretion": No IG, no Court of Inquiry can review the NTSB-staff errs.