The NTSB redacts the names of individuals. None of the names Boeing hands over will ever be known to the public. No one will know they were interviewed by the N

The NTSB redacts the names of individuals. None of the names Boeing hands over will ever be known to the public. No one will know they were interviewed by the NTSB nor who said what (even Boeing won't know that). At worst the final report will say "Engineer 1", "Engineer 2", etc. It is deliberately done this way to avoid the issue you describe. If people knew talking to the NTSB could get them doxxed and fired it would make cooperation impossible.