I actually understand your point. Tallest Skil seems to think along the same lines, even giving days in comparison. 😉
I remember stumbling on an article that indicated Apple would use DDR3 in the next MacPro. It was mentioned in one of the other threads, but I don't know if a link was given. 😱
Beckton is stated to use FB-DIMM2. 😱 (See wiki link in previous post).
It also makes sense to use Gainestown for another reason. Beckton is meant as a multiprocessor (as in four, min.). It may be possible to use only two Becktons together, but would likely not use their full capability. So to me, this makes for a more difficult and costly design, for little if any gains, IMHO. 🙁