Yeah 19 or 20, you're still growing, and have a lot of muscle development to go. He's not a half, so he needs every muscle he can get when a 115 kg front rower comes knocking. Looks big in the video but there's a lot of young small players around him.
What worries me is that he'll bulk up and lose that little burst of speed, he uses to break tackles. He's too slow for the backs. He starts going for 20 metres or so, but soon loses out to others (mind u I'm only judging it from the video). Plenty there for a good development coach to work with, in a young player, though. :)