It’s not like Chan was the first to do the outtakes thing at the end of movies, ya know. Burt reynolds movies had those outtakes at the end and I seriously doubt he was anywhere near first.
Chan uses the ones in which he's the one that mostly gets hurt doing/choreographing stunts.
Jackie Chan got the idea from Burt. Jackie was in CannonBall Run, saw the outtakes at the end of the movie, and started doing it himself.