If a book isnt paying its not because they are a scam or "holding out" as you put this... they are waiting for the REAL result.
As frustrating as it may be to everyone holding a bet slip, this is the right answer. There's a while to go before the official process is done. Sites that have already paid out did their users a favor.
And it's not like it would be a world's first if things went sideways during an election