Hi,
The "secret catalyst" whose function was to efficiently split hydrogen (according to Sergio Focardi) was most certainly a variant of these iron oxide catalysts.
For some time Rossi worked with Focardi, and Focardi worked with Piantelli at one point. Piantelli has been pursuing nickel since at least the early 90's. What you say may be true, but absent further information, I'm guessing Rossi has been working with nickel since he started collaborating with Focard, or perhaps even earlier, as nickel was kind of an Italian thing.
Hydride-forming transition metals cause hydrogen molecules to split upon adsorption, and a surface free of impurities increases this capability.
There is evidence that impurities are possibly important, e.g., as summarized in Ed Storms's reviews.