I dislike that statement, too, but for different reasons.
The 30,000x larger sample in the aggregate means the calculated fire rate for non-Tesla cars is probably a more reliable number. Maybe those 100M Tesla miles were "lucky"? Possibly not, though - I don't know enough about cars to guess.
The 3 trillion aggregate miles includes a lot broader sample size of car age than those from a single company that's 10 years old. This, to me, seems important to control for.
Finally - I bet the usage profile of a Tesla is different from the median usage profile of every random car on the street and throughout the country.
The 30,000x larger sample in the aggregate means the calculated fire rate for non-Tesla cars is probably a more reliable number. Maybe those 100M Tesla miles were "lucky"? Possibly not, though - I don't know enough about cars to guess.
The 3 trillion aggregate miles includes a lot broader sample size of car age than those from a single company that's 10 years old. This, to me, seems important to control for.
Finally - I bet the usage profile of a Tesla is different from the median usage profile of every random car on the street and throughout the country.