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Yeah, going by the rules as they are printed, Noxius does not interact with Bestiae at all, or any of the other sub-schools.
His ability is that he can count as any school when you are looking at whether you qualify for benefits from 75% school inclusion. So the ability is only relevant for those benefits where 75% school inclusion is actually a criterium. Which is LM, Legio, Morituri, Zephyri, and Helleniki.
His ability does not allow him to count as a beast or as Anum. Therefore, he can never be in a cohort that has the Bestiae benefits, since that is restricted to only beasts and Anum.
Of course, you can house rule anything you want.