Interpretation is difficult work, and typing makes it even more difficult. In person, people who are holding a conversation across a language barrier with the aid of an interpreter have to wait for things to be repeated back and forth, and such a convenience isn't there in a 90-minute talk.
Square Enix is not some massive multi-national corporation or big news organization that can afford to hire such gifted interpreters for a live web chat. It would be great if they could do it, but it just doesn't seem that feasible. It's impressive enough that their localization team can handle things fast enough to get patches out simultaneously.
Spoken like someone who truly hasn't even attempted to learn another language. Translations that take weeks are often still inaccurate, because translation is an art and not a science. Languages may be equally complex, but their parts never correspond one-to-one.
It is impossible to exactly convey what someone is saying in another language, and all translators are working to recreate the intent/meaning behind words. The less time given to make these adjustments and rework sentences, the more inaccuracies will arise.