Yeah, withdrawal delay happens for two common reasons in all casinos and websites (even exchanges). One of them is for hot wallets to be filled which is quite common everywhere and it is kinda not in their hands to have a hot wallet that empties faster than expected due to some whale withdrawing for example, but as long as they fix that issue there is no problem to have, eventually they will fill it and they will send it to you anyway.

Second and common for the casinos is the double spending method, many scammers send money, gamble, if they lose the money is not gone anyway, if they win they both keep their own money and also try to get the win as well (even if they don't keep their money). So long story short they have to check if you are one of them or not, if not then there is usually no problem at all.