This could be solved easily I think . Their rules could include this for ex: all bets entered 30 minutes before bet outcome is known will be cancelled and refunded with a 1%.
Timing does not work in Bitcoin the way you intuitively imagine it would.
In fact the reason the blockchain even exists in the first place is that timing and synchronicity issues have no easy solution.
I'm not referring to bitcoin or blockchain timing. I talk about bet closed time in bitbet.us. If they just reject those last 30 minute (even confirmed) bets, I think this will keep away cheater's bets and scammers.
I'm sure there's solutions. But seems like they like the actual betting system.