As we know that most gambling sites will require you to gamble and wager your whole balance once, before you can cash out or withdraw from the gambling site and they take this measure so people do not do money laundering whereby deposit and withdraw without gambling.
Now the point here is that on the gambling site, there are many easy winning bets with odds like 1.01x etc. If the money lauder is sensible he can easily be wagering the whole amount by placing a few bets where the odds are very low and the winning chances are 99%.
So does this mean that there is a loophole here and the money launderers can easily by pass this wagering requirement?
If it's a loophole, then all people must have thought about it besides the casino team itself. therefor they surely won't allow anyone to use this method to escape and trick the requirements and prevent money laundering systems. Wagering requirements are usually imposed only on large funds and deposits (legit casinos at least) not small amounts. And Logically nobody would attempt to launder a sum as low as $100 or $200 in a casino.
beside that risking more than $1000 in a casino and regardless of the winning percentage (as long as it's not 100%), should be enough to avoid money laundering especially for large sums of money. But nowadays there are other loopholes available to evade these rules and law enforcement which only few people knows them.