I have a couple of questions on this:
1) Firstly, can they be absolutely 100% sure that FD didn't view the video? Do all views get logged even if the viewer was using some kind of anonymity techniques?
2) Were the tests conducted and reported multiple times against the same account? To me, it's pretty obvious that FD are not going to take any action against any player for a single (or even several) reports of combat logging.
Fundamentally, video evidence or not, it's impossible to conclusively prove that someone combat logged in a single case, since they can just say their internet went down, and no telemetry or video evidence can prove otherwise unless FD have a camera in their house.
Seems to me, the only way FD can handle this (if at all) is to track all reports of combat logging, and then look at it further when the same commander is reported multiple or many times. They probably have a limit on which they only look into it if the same player is reported more than x times, and x is probably quite a high number like 10 or more.
So it may also be that your tests didn't trigger the number of required reports against a single account to warrant further action. Until it hits that trigger, there is no point reviewing video evidence. Granted, if the person admitted to combat logging in the chat, and that was shown in the video, that is bigger evidence, but I highly doubt that they would operate a single strike policy anyway - even if the person admitted it they probably wouldn't ban them until they did multiple offences.
Also, you don't say whether perhaps the person doing this in the first case didn't even realize it was against the game rules.
Edit: Personally, I don't like Combat Logging and I personally wouldn't have an issue with a system where if you combat log when you are in combat, you lose your ship. You would then be allowed a number of "get out of jail" cards per year where you can get your ship reinstated - this should cover you for when the disconnect was truly not your fault. Personally I would be ok with that, but then I have a good connection. If you have a really dodgy connection, probably you won't like that solution.