This phenomenon of "early departures" is now pretty common: I've taken off 3-10 minutes early on several occasions since about 9/20. I guess when you've got the plane loaded and the seats full with every checked in passenger, why not?
The "ON TIME" arrivals figures are bunk now. First, the airlines themselves have lengthened the "time" for all their flights over the last 18 months! Surprise! Now with fewer flights and less taxi time, you're in "early"!
Don't kid yourself: SFO and LAX did *not* get further apart, and planes don't go slower these days. They just built the atrocious delays into the schedule, and now we're getting a little relief. When they go back to honest scheduling once again, to reflect the reality of today's lowered flight volumes, the "late" will be the "late" again.......