One can only speculate that without airdata, the RTLU was not in fault, but couldn't compute its limits due no speed data. Not being in the set doesn't mean it is inop, per se. It rather defaulted to least sweep, due last velocity, M.82. I think this is the working theory. There is no reason to exclude extensive damage to flight surfaces, without loss from airframe. The VS roots look as though they encountered a range of overstresses, perhaps it "broke" on board, to remain onboard to the surface. If broken loose, (not 'free') and inarticulate, serious inflight control issues would ensue, etc.
As to in-flight breakup. Yes. And No. There was no disintegration. There was the opportunity however for shedding some parts due air loads (overspeed) or cycling at past critical limits (airspeed). Found on the surface were flight surfaces, aileron, elevator, and spoiler, and radome. The drift calcs are inconclusive, and there was ad nauseum comment on the issue, some of it mine. If the ship plunged quickly down from LKP, yet ended up in a flat spin (aspect), remember the average rate of descent is 6,000 fpm. Likewise, the average AOD is 45 degrees (down) plus, pointing to the possibility that some nose down may have been in excess of 50 degrees or more.