That free AML tool is actually helpful for normal people not experience any possible issue with the casino.
But it also have a downside, since scammers can actually use that free tool they provide to possibly now that their funds has been detected. Then change their strategy and find other best alternative route to escape and withdraw their stolen funds.
Knowing or tracing the origin of funds is common knowledge, and besides, there are paid AML screening tools out there, so scammers will still use those. The issue here is for the common users to know exactly what kind of funds they are going to deposit in an exchange - Does the exchange consider their funds "clean" or not?
Imagine depositing funds you received from another service only for the exchange to block them, stating that the funds is from stolen sources. How will you prove that you are not the hacker?
But if you use the AML tool provided by the exchange, before you even deposit the funds, you will know that the money is from illicit sources