Adding to derail: German version goes with the term for young man as well, hinting at him being anywhere from 18 to 27. He was younger than most of the Convocation, but that was about it. We see in Amaurot that Amaurotines act way different when addressing actual children.
Him being that small after Seat of Sacrifice is most likely clever symbolism of how much of 'him' was lost over the years as Zodiark's heart.