Yeah, I agree mostly, but I think you may be overlooking the compression of your sleeping bag as part of the sleep system. The stiffer distribution of the CCF pad will also cause increased compression of any insulation, synthetic or down on a specific area, like your hips, and shoulder or buttocs and shoulders. It might very well negate any real R value increase due to distribution of loads. It might not, too. Roger & Will admit to having some strange results testing the Klymit pad, as an example, that uses part of the sleeping bag's loft/insulation to warm a sleeper. (Thus achiving higher R values than a simple pad test will indicate.)
One of the problems I have the testing of the individual gear items, pads and R value in this case and as Roger & Will have done, is that it does not test other related items a hiker/camper uses to perform a task. Focusing on R-value of a pad, and adding them up, does NOT necessarily give a true picture of the entire sleep system. Distributing compression across an air pad will help. Focusing on order, as you say, makes a slight difference with two different pads as the OP was taking about.