It's really just like beak maintenance guys. Mine does it (honing the nails) while preening and sitting in the sun...just about the most relaxed state he's in. Here is SOMETHING to watch for. Nails trimmed to far, not allowing curvature to maintain balance on various sized perches. In the old, lengthy quarantine days, they trimmed nails once for the entire quarentine period. This bad technique has translated into how closely vets trim. Ever notice after a MAJOR trim, how your bird will mouth at it nails without really doing anything? My beleif is that there is "phantom" feeling of still having the longer nail.
Yeah, my arms used to be a wreck too, but I just don't let Lucky stand on my arm all day...He's got stuff sort, chew, and toss about!!!