It's true that they've had the conventions themselves ready since March, but not the lore behind them. I can go and dig up the post if you like.
With that in mind, the lore behind the clans could very well color players' choices on which tribe to go with and what to name their character. Your average player doesn't really care and just goes with whatever they think is cool and/or sexy, but some people do. It's not really the names themselves holding it back (as far as we know), but information on the clans beyond the most basic of outlines of their social structures. And while Raen names have solid guesses based on in-game Domans and Yugiri ([Japanese name] [Nounverb(er)]), for all we know the Xaela have their own pseudo-language like the Sea Wolf Roegadyn.
Yeah, posting what they have would assuage the irritation of the people who it's been translated for, but it would further irritate the people who don't have it yet. While it's extremely irritating to be so close to the wire and still have nothing but gods-damn "soon™," at least everyone has "soon™" so it's fair.
That said, the post from Koji is back from mid-March, before 2.5.5 was even released. I don't think it was crunch time back then? /shrug. Either way, they've admitted they're at fault for screwing the pooch on that one, so all we can do is wait with bated breath for soon™ to come. Being upset and impatient isn't going to help.
EDIT
Here it is (with the relevant information):
Dated March 8th. My birthday, coincidentally.