An F-16 can turn fast enough to make the pilot black out of suffer severe injuries; one of the things the software does is restrict G-forces to acceptable levels. As potentially terrible as this bug was I've never seen any indication of where in the development life cycle it happened; it could have happened early on when it wasn't meant to be working yet (i.e.: working enough to fly, but with no handling of edge conditions worked on) or it could have happened in final testing of a release candidate.