Well, CC is a stretch as re 447. Stall and upset are not, and the U-2 can be flown (is) manually on the edge. It takes a lot of training. Not long ago, a U-2 pilot did something most pilots would have said was nearly impossible, he Stalled, and Spun, while turning Final at Beale. He crashed in town, I think, but with the lift the a/c has, and the glide, there is no excuse for stalling a wing. Especially when one can control the a/c at the razor edge in thin air. Beale is virtually sea level, and the weather was nice. This aircraft gives up and drops a wing on the Runway slow enough for E-1's to run along it and grab the tip, to keep it from scraping concrete. Landing is actually the most difficult manouver in the a/c's quiver. It was designed w/o focused attention to landing, other performances were critical. It simply does not want to stop flying.
FBW actually does make possible flight beyond the safety limit for manual control. It isn't advisable, but as BOAC has said, it promises alot. At the edge of a Stall, the FBW machine won't burp, or sneeze or suffer nervous muscle contraction. Manual limits are grosser, this is why I think numbers can be calculated for this test, and flown down to prot (calculated prot). The computed number is accurate, and should be relied on, but the crew here did not take the time to calc this low speed number.
It really is as BOAC says, and I don't think he would disagree that FBW can glitch, meaning the pilot must be schooled in Glitch response. I disagree that the glitch is in any way different from any other machine. The fault lies in unjustified reliance on the machine, based on its representations, instead of scepticism, and proper training/response. IMO.
bear