The other option is that a lot of modern high horsepower drag cars have an on-board computer data logging system which a crew man switches on as the car stages (external switch at the rear somewhere) - possibly he triggers this to get a second independant record of the event!
No crew contact with a staged car has ever been allowed.
High horsepower cars now generally do a rolling burnout rather than a line-locked static version - i.e. wet the rear tyres and floor it between the tower and the lights. Up to half track for the top guys, laying visible strips of hot and fresh rubber across the start line. And doing a lot of crowd pleasing and all-round showing-off, of course!