Personally I think it's an acceptable observation. Even if reduced levels of dietary fructose are not directly responsible for their health, it seems extremely feasible that an ordinary person could elect to follow the model of avoiding fructose, and expect to benefit, because they will replicate the patterns of fructose avoidance, healthy-food-selection and all.
Do you see what I am saying? The two unique features of these people are fructose intolerance, and avoiding fructose. Unless fructose intolerance confers health, the act of avoiding fructose must aide in health. The precise reason for the improvement in health isn't important, if all you (on an individual basis) desire is to replicate their healthful results.