Let's say this.
You guarantee players that they get paid if they play at the casinos you promote. You are promoting them, telling visitors of your website to play there, so not so weird if you trust them that much that you would guarantee this. If they win and do not get paid, this guarantee means you have to pay and claim your money at the casino you are promoting. Let's say up to every 5 digits prize and every obvious breach of any clear T&C-term excluded.
Would you do this?