I don't know what a fuel catalyst IS, but a 22RE will run unleaded fine. Given that LRP is basically unleaded w/ a higher octane + valve seat lube stuff anyway, I don't know what they are on about.
Though, regular unleaded has a lower ocatne rating than recommened I think (91/92), so your better off sticking with LRP @95/96 for the money rather than paying an extra cent for premium which is about the same.