Keyword "seen", not did. Until you step up to play for 10k you don't know what it's like.
There is no "man's word" when it comes to gambling. If a guy calls off a bet BEFORE the match or game starts then it's off.
You think I can't call a bookie and lay a bet today and call it off tomorrow? Of course I can, for the exact same reason I could call him and bet more or even change my bet to the other side - you can do anything you want BEFORE the match starts unless you froze up the money and the terms before the match.
That's WHY people freeze up the money. That's WHY people make stipulations to that effect.
That's WHY people can change their bets, change their minds, bet or not at every casino on Earth UNTIL the dice are cast, until the ball drops, until the cards are dealt. Until the money is posted or the game has started then any side can change their mind.