I don't think I've seen any evidence to suggest that "gifted kids almost always have lower processing and working memory scores."
By "lower," I don't mean "lower than average"--lower than other scores? I thought it might be a function of these kids being harder to serve, too, but a quick Google seems to reveal that the conventional wisdom is that processing speed really is often relatively low in gifted kids...or it's low by the measures commonly used, anyway. I agree that these measures may be off in some way.
Kids who look like that make up a large majority of the kids in our local GT/accelerated classes b/c they have the high achievement (grades, NCLB test scores) to get in.
I was wondering just this--are these the kids who score high on achievement and not as high on IQ?