When you're playing candy crush and FSD kills someone, whether or not it's drives better than the average driver is not something the judge and prosecutor are going to consider.
First, that’s because FSD is legally only L2 and thus legally you are required to pay attention. It has nothing to do with the engineering realities of the impact on improving safety.
When L5 becomes available then this becomes a different calculus. And it’s honestly questionable about how good the characterization actually is since Tesla’s L2 FSD seems to outperform Mercedes’s L3 and it’s more a matter of the liability the manufacturer is willing to take on vs objective measurements of quality.