WM, That siliqua may look like Arcadius but as John has said earlier, the busts were very stylized. If we did not have the obverse or reverse legend we could not properly I'd the coin. For example look how different the busts are for Magnus Maximus and they were both were struck at the same mint.
Indeed it was a scarce thing to have an artist {graver} who knew the real face and had the talent to do it, but it did happen sometimes.