Ohh -- I don't think I've come across those characters so much. (I'm not new to manga, but I haven't read much overall.) I can think of one, Tzaphkiel from Angel Sanctuary, and that scene helpfully shows how he is tricksy like a fox. Beyond that, I can't really comment; not enough examples. Too bad -- there are probably a lot of interesting reasons for why the prosthetic limbs are cool.