Use up all of a currency even if not enough for bill


Assume you have created a number of currencies eg base currency - GBP and you add US dollars
You have a bill for 50 USD - your dollar balance is 25, so use all of that and then convert another 25 USD from your GBP balance. Currently the logic is to use the GBP balance to pay the bill since there is not enough USD available

I thought this was a MasterCard restriction, but I noticed my TransferWise card did as I suggest above