I have another data point for this. I was doing a transfer from Georgia to UAE. USD. They asked for documents, including some that don't really exist (bill of lading for personal purchase). I said that I can't produce those documents and that the request was strange. The bank answered that they agree but they would not be able to make the transfer for me. Then they offered to convert everything to AED. I agreed and the transfer went out with only an invoice required. Easy, fast. So, I believe it was a requirement imposed on them and USD was the reason. Cheers.