Historically these kinds of assertions have been quite misleading. If FSD is mostly used on highways and other "low complexity" environments and then you compare that to human collision rates in
all environments,
of course FSD will be "safer". Especially if you're measuring collisions/mile vs collisions/hour. Then there are other confounding factors like how Teslas are:
* Generally newer than average.
* Generally owned by more affluent drivers than average.
* Probably used predominantly in urban areas instead of rural ones (to be clear this might unfairly tilt the stats against Tesla thanks to the highway thing).
I'm not sure I've seen a good "apples to apples" comparison on this that corrects for these confounding factors.