Was the 'sixth generation' boom really such a smart idea, given that the KC-767 has been refuelling with the 'fifth generation' boom ever since 2007?
The KC-767 boom is based on the KC-135 boom. The KC-46 boom is based on the KC-10 boom. Those are very different booms. The change was required to compete with the KC-30 boom and to meet the latest operating envelope requirements imposed by USAF.