That $9.6T is mostly back and forth non-directional HFT.

Otherwise it would not take a day to swap $500 mil for commercial reasons (think buying a couple Boeing plane with Euros) to avoid too much market impact as documented in multiple interviews with currency dealers stating it takes them 1 day to "work" a $500 mil order.

Retail can move FX, if it piles into one pair. But unlike the Boeing order they will also need to exit the trade at some point, which makes them vulnerable.