The MRTT is a reasonably straightforward development of the A330-200F, which in turn is a normal, commercially certificated freight derivative of the A330-200, which is a successful airliner. Yes, there are genes from the A300/320 in there, because that's the way Airbus grew the family, but it is in no way comparable to a 767-2C.
We'll have to agree to disagree on that. The A330 sprang directly from the A300B9 and the A340 from the A300B11. The B9 and B11 programs were merged and renamed TA9 and TA11. The fuselage and empennage and many (most?) systems came directly from the A300, making the A330 essentially an A300-600 with two additional barrel sections and a new wing, but one based directly on the A300 wing after the variable camber wing and laminar flow wing were both rejected. The A330 freighter door came directly from the A310 freighter, and the A330's avionics came directly from the A320, including all the displays, many cockpit panels, and the sidestick controllers.
And I agree, this development cycle and pedigree is "in no way comparable to a 767-2C." Boeing definitely uses a different approach. But since the A330MRTT uses bits from unrelated airplanes and even held over bits from now dead airplanes, that seems to me to be far more Frankensteinish than the KC-46 which derives its bits from various versions of the still alive 767.