I doubt it is rollout, the difference between a "normal" rollout and a "two block" is a matter of a few feet. As energy to be dissapated increases the rollout does not change significantly, just the speed at which the valves close.
I think it was just more of a case that the A-12 was so big and came aboard so fast, it was too much energy for the system to absorb. That POS was so far over weight and approach specs, it was criminal. ADM Dunleavy pissed off a lot of people when he CNXed the program, but at least he had the balls to shut down a program that was waaay out of control.
If only someone had done that with the Hornet...