Having taken graduate-level aero courses and specializing in dynamics in general, I can tell you that the information here is not technically complete enough from which to form an opinion (as is usually the case with this sort of info).
Yes, fighters and commercial airliners can sustain far, far more than 0.8 g's. However, acceleration is a vector which has both magnitude and direction. They are giving us only magnitude.
No commercial plane that I know of can sustain more than about 2 g's in a yaw-only induced turn without having problems. Think about it - twice the plane's weight applied only to its vertical tail surface. It's not that big a stretch to imagine if the tail fin had already some stress concentration such as a damaged bolt, that it would rip off in a 0.8g yaw-induced turn. In fact, I can;t imagine any pilot directing his plane to do so, but it is possible that wake turbulence alone could cause it.
What is unlikely is that the plane was executing a proper turn - ie, roll + yaw, and fell apart at 0.8g. That would mean that the wings would fall off, and the plane would have likely not gotten off the ground in the first place.