They went from -0.1% to 0.1% to 0.25% now. It may not seem like much, but the latter is a 2.5x increase, the former, well...

In any case it appears to have caused an unwinding of the yen based carry trade, i.e. borrowing in JPY and using it to purchase foreign stocks/bonds/etc. The unwinding leads to a stock sell off, and a lot of yen buying to settle those loans

Right, the article doesn't make sense. The Yen jumped on the rate hike (meant to combat inflation.) Both the hike and the increase in the Yen is going to result in an unwinding of the carry-trade. This then puts further upward pressure on the Yen as investors buy Yen to pay back those debts.

BoJ interest rates went from <0 to >0.

With a sentiment shift like that, the decimal numbers themselves almost don't matter. It was guaranteed to result in a shakeup.

Correct, everything right has to do with Bank of Japan moving to strengthen ¥ as it has lost over 40% of its value over the last 3 years. Many people using it as an interest free loan to trade are having to quickly unwind positions. This of course creates a temporarily unstable market that’s highly volatile as it finds equilibrium.

I expect the FED to announce a 25 basis point cut this week.