So maybe the difference between Sue and Grif's experience is heat? If our cladding has the same issues as GM cladding, which is to say contaminants are driven to the surface by heat, you would have to assume that process is occuring much faster in Arizona than in Washington or Alaska. So maybe the extreme heat drives the contaminants to the surface, which then undermines R/R's chemical bond with the cladding surface, which in turn causes it to be brittle and easily flake at the smallest impact (bugs, etc.). Just a theory anyway.
And lighting/angles definitely make a huge difference in how your cladding appears. Take the three photos below of my "darker" cladding for instance. Photo #1 shows my cladding without any treatment whatsoever in the shade on a sunny morning. As you can see it looks horrible, and has a similar blue-ish hue to Sue's cladding (at least that's my perception). But if you look at picture #2 the cladding looks much darker, when in fact the cladding is completely untreated in that picture as well. The difference is that although it was also a bright and sunny day, the sun was not quite directly overhead, so the cargo carrier was casting a bit of a shadow over the cladding. In picture #3 I had just treated the cladding with B2B, and when combined with overcast weather, it's probably the darkest my cladding has EVER looked.
Sue, I obviously haven't seen your VX in person but I don't know that I buy that your cladding is somehow different in composition/pigmentation - it just seems too unlikely that you'd be the only member experiencing the same problem. Personally I think it may be that you haven't yet found the right product for such a hot and dusty environment. I would definitely try to find a way to remove R/R so I could try other products. Do you think paint thinner/stripper (diluted) might take it off?