Buyer Assignment Rules ignoring functional currency

We are seeing an issue where the Buyer Assignment Rules seem to be ignoring currency.

For context, we have all orders over 25k auto assigning to a specified colleague. The currency column in the rules shows GBP and isn't editable and the functional currency of the BU is of course GBP.

However, today a user raised an order which totalled 60k JPY which converts to just over 400 GBP. The rule shouldn't be triggered but it seems it was as it auto assigned to the aforementioned colleague responsible for 25k+ orders. I've tested to ensure it is the amount triggering it as this is the only rule the colleague is assigned to.