Fiatleak is an illusion. They don't have real data about currencies flowing into and out of exchanges. They have only the trade data from exchanges, which most exchanges make available. If someone trades AUD and Bitcoin on an exchange, they show that as AUD being invested in Bitcoin. If the same AUD and Bitcoins are traded again, they show it, again, as AUD being invested in Bitcoin.
If someone makes a withdrawal from an exchange, they don't know about it. They show all trades as buying into Bitcoin. That's why Fiatleak is an illusion.
They have cool graphics, but the conclusion they draw from the data is bogus.
I have also said that their data is completely wrong. The concept and looks of fiatleak are great, but there isn't any real (useful) data being displayed.