I am not a lawyer, but I don't imagine they would want to have documented, in writing, that they knowingly broke export regulations for one week.

If the issue is knowingly keeping someone on the platform, then why did Fedora have to acknowledge that they knew of this user's existence at all? Could they not have kept 'unknowingly' allowing him to have an account? They did for an X amount of time already, obviously, why not for a longer Y amount? What's the difference?

The issue is not them knowing it. The issue is that it is illegal, period.

If you do it knowingly, there may be additional provisions that you're breaking, or additional penalties, and you increase the length of time that you are out of compliance. This doesn't mean that you're totally in the clear if you "didn't know", which would be hard to demonstrate anyway, considering their own wiki had this information listed.

Fedora is part of Red Hat which does a lot of business with the US government.