I don't disagree.
The "official" role of the manufacturers is to provide "technical assistance" to the NTSB; to assist the NTSB in understanding how things work. Slant and bias are a part of life but the NTSB's goal is to avoid it by limiting the participation"
Only those party employees who have suitable and needed technical qualifications will be permitted to work on the NTSB investigation.
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...corporate executives who will not be providing needed technical expertise as participants on an NTSB investigative group are not permitted to participate in an NTSB investigation.
By statute, NTSB reports are generally inadmissible in accident litigation and the NTSB rules further that statutory policy by limiting NTSB investigator testimony in those cases to factual content, and "shall not give any expert or opinion testimony."
Nothing is perfect (and there is often litigation about the extent of the preclusion in specific cases) but the NTSB has historically gone out of its way to protect the neutrality of its investigations.