Comment/Bug? (Procurement)

UBL 2 prd2 cd1 Comment (Procurement)
There seems to be a possible bug in the OrderChange and, to a lesser  
extent, in the OrderResponse
concerning the Parties:
1. AccountingCustomerParty is optional in Order, mandatory in OrderChange
and missing from OrderResponse
2. OriginatorCustomerParty is optional in Order and OrderResponse but  
absent from OrderChange

All the best

Stephen Green