True, however the big difference is that with the bare-chested pirate, there is no explanation other than "I wanted it that way." If a human pirate isn't wearing armor or using magic, and doesn't have some fancy prestige class, then I would call foul.
However, I have no problem with DM Fiat if there is an actual explanation to it; maybe the pirate has an obscure template or prestige class. Perhaps the human pirate isn't human at all. Who knows? The point being, if you want to have a bare-chested pirate with a high AC, use the rules presented, even if you have to make up something new. Don't just hand wave it with your mystical DM powers, that stinks of cheating a laziness, IMO.