You can't read into it much for such a low volume exchange. It's akin to a small sample size resulting in behavior that can stray farther from the mean. This article also makes a glaring omission of using the Tether/USD index price (since Kraken is not the only exchange trading the pair), so prices can move in the market without any volume occurring on Kraken, if the traders shuffle the orderbook before arbitragers make trades.