There is certainly a definite retarding force from the 737 reversers, PJ, which you will sense when you cancel them. However, the braking action reversers provide will be nowhere near the 'target' for the brake setting so I cannot see how the AB light would illuminate if the brakes were ineffective.
I am still wrestling with the fact that (apparently reliably) the a/c impacted the building at 94kts? The a/c would certainly have been travelling at 94kts+ as it reached the end of the runway at CGH. I don't know a MLM Vref for the 320, but let's assume 140kts? Let's also give the crew a 'fair go' and say they touched down 1000' in at Vref. 5000' later they have only lost around 40kts? Drag and rolling resistance, even without a single reverser, would surely do better? There HAS to be significant forward thrust there somewhere.
When do we expect an interim report?