Also the Japanese KC-767J had an AAR boom, so quite why it has taken so long NOT to fly a KC-46A is perplexing in the extreme.
The boom on the KC-767 came from the KC-135. A heritage Boeing product.
The boom on the KC-46 came from the KC-10. That's a very different boom and a heritage Douglas product.
And the biggest change to the KC-46 is in the Mil Spec wiring. Mistakes there cost months to resolve.