The accident resulted no on-board passenger fatality, so it does

Although a ground person was killed which is a tragedy without any doubt. but technically speaking, the statistics is about the safety of the airplane passengers.

Quoting the description in wiki, "The accident involving Flight 1248 was the first Southwest Airlines accident in the 35-year history of the company to result in a fatality", confirming the safety record of Southwest.

Thank you for the info. It is a useful data point.