I think the NTSB would probably love to interview to the crew who actually used the tools--even if nobody can figure out which exact team used the tools on this

I think the NTSB would probably love to interview to the crew who actually used the tools--even if nobody can figure out which exact team used the tools on this exact plane--they probably wouldn't so much as incriminate themselves as to paint a picture of incredibly shoddy quality control. Instead carefully parse that phrase "names of Boeing employees, including door specialists, who we believed would have relevant information" which are all likely management / project-management kinds of positions who are vetted by Boeing.