It peetty much looks like that; Boeing admitted there is no documentation to come by, it was not the only time the mistake happened and we have rather credible whistelblower. Add to that a DoJ investigation, and the above looks like a realistic scenario.

We will know once the FAA and NTSB did their investigation and audits, and published their reports.

Just to repeat: When you work in aerospace, you do not work on an aircraft without documenting your work and any deviations or non-conformities. Period. And even if you are forced and pressured by higher ups to do so, you do it properly. The fact that we have a whistleblower tells me rank and file are less than happy with the status quo so. Doesn't change the fact that someone made a serious mistake working on an aircraft. That alone is serious, even if it wouldn't have resulted in an incident.