As someone who primarily plays Maori, I find this super annoying. If barbs are only supposed to get quads when half the civs have shipbuilding, then it sounds like it clearly is a bug. I always just thought as soon as the first civ got it, they did, and so it was something the Maori just had to deal with.
But it can really hurt one of Maori's biggest advantages, because sometimes my units and fishing boats are harassed so much I can't even explore or improve my sea resources, and I have to start producing a quad or two of my OWN just to defend. They take a lot of production to make for that early in the game, don't feel as strong as land units, can't travel as fast (for Maori), and can't heal outside of a city. It just feels bad to make them and a waste of time and production. I mean, I'm used to it by now, but it's still annoying. lol