Why If we go to Home-> Resource -Management -> Resource Financial subpage -Supplemen -> Vendor for the expense resource, we are able to remove the vendor and save. However, when we do it through XOG setting the value setting the vendor code to a blank value "", it will not set it to a blank value.
Release: Component: PPMXOG
Even though I am able to reproduce this behavior in my local environment, it is by design. XOG is not designed to delete values and I know you are able to delete via UI and that's fine, but UI and XOG do have different business rules in some cases. We had a defect that was fixed in 15.3 which allowed to delete Vendor code if it was missing in the input file, see DE31732 - PPMSAAS_15.1_DEFECT - The vendor attribute(vendorcode) is blanked out from the Resource Financial Properties after a resource XOG if not included in the input file.