The FBI will investigate the factual circumstances only and present those, as they are able to ascertain them.
There will be no conclusions, as reaching conclusions is not their role when conducting background inquiries for an intended federal officeholder.
There is no issue regarding probable cause/warrants, and the FBI has no jurisdiction over a state level crime. They will not be conducting a criminal investigation, but rather extending the background investigation already undertaken into Judge Kavanaugh.
Those specifics aside, anon’s analysis is plausible.