But then it hit me!

They can actually check if you're going through the impractical ceremony on not! I verified this by checking the network requests, and AFAICT the only way to view the server-seed hash is via a network request to "/ajax/modal" with "modal=fairness".

So this means they can actually if you're verifying the bets or not. So they could trivially cheat only when they know you won't be able to tell (when you never requested the server-seed hash).