Well...keep in mind that the FAA does not perform the formal accident
investigation. They do the initial fact-finding, and all the analysis and
determination is performed by the NTSB. While they are both government
agencies, they are quite separate. You'll often find the NTSB reports at
odds with current FAA regulations/policy (almost always towards trying to
make them MORE restrictive, but, hey....)

I know of one case where the FSDO investigated, turned the facts over
to the NTSB, and the NTSB conclusion changed the facts to support their
conclusion.