They were doing some construction on 28L a while back, but I thought that was supposed to have been completed at least a month ago. Construction was on weekends, which matches the Friday evening timing.
When no construction was happening, I've only ever seen aircraft line up directly alongside 28L, which I believe is 28-F (for takeoff on both 28L and 28R), so multiple aircraft on 28-C would also match up with the construction theory. Then again I've never been at the airport around midnight.