yes, and it proves GP's point about crypto enabling crime. It's trivial to implement.

It's just a ledger kept outside so there is no link between the money going in and the money coming out.

Money laundering involves the intentional hiding of the origins of funds obtained through criminal activity. Attributing the source of funds as being criminally obtained is difficult if tumbling is done effectively. If tumbling was reason enough to be suspected of money laundering, so would splitting a $100 at a gas station.

Not necessarily, if the source of the money is legal and you're tumbling it just for privacy reasons, it's not money laundering.