I’m on the precipice of testing this…I don't think that was ever said. I think it was just that you needed a minimum of 100 miles before your score is valid. It is a 30 day rolling window, not a 100 mile rolling window. I'm not sure what happens if you drive less than 100 miles a month though... Does that counted milage also roll out of the window after 30 days?
A 525 mile 87 score day rolled off this morning taking me to 100 over 417 miles. Tomorrow a 397 mile 100 day rolls off leaving me with 20 miles total @100.
So, if 100 miles is required, I need to get FSD today.