Booking RT using FC miles

Dear Guru,
Can you please cite me (chapter and verse) VS FC policy re booking partner flights? Am told by VS that must book return flight (told not allowed to book single sector using miles--which seems odd a shave done so many times previously) and ...if no business class available return but reluctantly booked outbound with Y return as PE does not exist (!) on NZ--must pay Business return miles (a hefty 125K) even though not receiving business product for 1/2 journey? Am told this is NZ policy but NZ say this is VS policy?
Gratefully appreciate yr response,
RR [?]
Can you please cite me (chapter and verse) VS FC policy re booking partner flights? Am told by VS that must book return flight (told not allowed to book single sector using miles--which seems odd a shave done so many times previously) and ...if no business class available return but reluctantly booked outbound with Y return as PE does not exist (!) on NZ--must pay Business return miles (a hefty 125K) even though not receiving business product for 1/2 journey? Am told this is NZ policy but NZ say this is VS policy?
Gratefully appreciate yr response,
RR [?]