Have you ever consider that casinos intentionally delay someone's payout specially if this is huge money? Reason being is that,
The longer the withdrawal is pending, the higher the chance the player cancels it and plays again.
And also, suddenly KYC is being asked after that big win, delaying it even further to the point that some gamblers be frustrated and just play their winnings until they lose everything back to the casino?
Well even if there's a valid point in what you are trying to explain, I still think it doesn't really apply generally. Well to start with only a non disciplined gambler I guess would go back betting after he previously made up his mind to withdraw. Plus if you check casinos are usually in constant competition for withdrawals and payouts.
Based on this most of them want to keep up a fast withdrawal reputation to ensure they can use it to their advantage in advertisements.