The average is not the only stat though, and doesn't tell everything. Even if it were true that FSD was safer than the average of human drivers, replacing some manually-steered cars with FSD cars could result in more pedestrians getting hit, depending on the breakdown within the two groups. The overall average isn't enough information and obscures the internal distribution of skill/safety within the overall population of drivers.
It matters who is driving what cars. If you're taking safe drivers and having them drive FSD cars, and comparing the average of that against the average of all non-FSD driven cars (which includes a lot of really shitty drivers in the average), then the net safety impact of this could be nothing. Introducing FSD cars would have no impact to overall car safety, and might even have a negative impact, if the FSD software is worse than the good drivers who are now not driving manually-steered cars but are driving FSD cars instead.
It matters who is driving what cars. If you're taking safe drivers and having them drive FSD cars, and comparing the average of that against the average of all non-FSD driven cars (which includes a lot of really shitty drivers in the average), then the net safety impact of this could be nothing. Introducing FSD cars would have no impact to overall car safety, and might even have a negative impact, if the FSD software is worse than the good drivers who are now not driving manually-steered cars but are driving FSD cars instead.