B2B Export - Customer VAT Reg nr

Could you please provide guidance on how to complete the AccountingCustomerParty segment for a B2B export tax invoice?
According to BR-KSA-46 we should not populate the buyer VAT registration number (BT-48) for export.
Do we need to populate according to BR-KSA-81 the other Buyer ID with the foreign VAT Reg number and Tax Identification Number “TIN” as schemeID?

To clarify the field names a bit more the question is weather we should use VAT number (registered) or Group VAT number (cac:AccountingCustomerParty / cac:Party / cac:PartyTaxScheme / cbc:CompanyID) or Other buyer ID (cac:AccountingCustomerParty / cac:Party / cac:PartyIdentification / cbc:ID) when we are issuing an export B2B invoice to populate the Customer VAT Registration Number?