“...perhaps the Gov sealed it to prevent some state employee from illegally releasing it and subjecting the state to a lawsuit.”
That is the most logical and likely reason; one I would bet on.
However, my out-of-the-box theory is that O got caught in a reverse Sandy Burglar operation. If born in Kenya, O desperately needs a US citizen father (Frank Davis).
By sealing (what ever the document is) the Governor has preserved evidence while awaiting for a member of Congress to object to O’s qualification - subsequent to the Electors delivering their certification to the Congress in December.
Last time I looked the law requires proof of citizenship or a green card before you can get a job flipping burgers at Wendy's. Am I missing something here?