I've not read the contracts or seen the aircraft, but I had heard that the RAAF KC30A was specifically ordered with the A340 wing - because of the extra hardpoints, plumbing and an extra spar. FSTA, on the other hand, was ordered with the A330 wing, to be modified.
The extra centre gear would be nice - don't both wings share a common centre section with space for the gear blanked on the 330? I would guess it was ditched due to weight penalties.
As for a name... The "A330 MRTT FSTA KC-30A KC-30B KC-45" is a bit of a mouthful.