Any idea why this request doesn't set the correct currency for vendor purchase price for an item? It sets the vendor's primary currency instead. The internal ID for USD is correct and the vendor has USD assigned as available currency.

<ns1:itemVendorList>
                   <ns1:itemVendor>
                        <ns1:vendor xsi:type="platformCore:RecordRef" externalId="c6eec474-7641-4796-9397-bcf1e3cb122b"/>
                        <ns1:vendorCode>RBC20J</ns1:vendorCode>
                        <ns1:vendorCurrency xsi:type="platformCore:RecordRef" internalId="2">
                            <ns2:name>USD</ns2:name>
                        </ns1:vendorCurrency>
                        <ns1:purchasePrice>227</ns1:purchasePrice>
                        <ns1:preferredVendor>true</ns1:preferredVendor>
                        <ns1:subsidiary xsi:type="platformCore:RecordRef" internalId="2"/>
                    </ns1:itemVendor>
                </ns1:itemVendorList>