This confirms other articles which I have read on the subject of the tarmac meeting and the FBI.
The FBI was not concerned with the obvious illegality of the meeting, they were only concerned that the meeting was 'leaked' and made public. Once again, they were acting as Hillary's staff instead of a government agency.
From what I read, they actually formed a team to investigate and find out how it was leaked and who was responsible. It was never made clear what exactly they were going to do to the person if they found him/her, but they were not holding anything back to find what they called, 'the leaker'.
Funny how the FBI would consider simply reporting on an actual event which happened in a public place to be a 'leak'. What was the FBI trying to hide?