The way I see it, Platinum 4 is a high rank with a high amount of wager requirement. With that amount of money for gambling, it should be pretty easy to prove your source of funds (for most whales) since you are expected to have six+ figures job, legitimate businesses, etc. Without that proof, there are only drug dealers and the like. Trading should be fine though if you have the record, should be treated fairly similar to this:

Source: ToS

Anyway, there's nothing to worry about for small-time gamblers since who cares about the origin of $100? It is only applicable to whales.