I noticed something screwy too yesterday. Many flights in September that were virtually empty all of a sudden went to almost full in F & J. Seat maps also went from showing large sections of blocked seats in J to showing them as all occupied. Seemed very odd; they must be tinkering with the system.

Edited to add: a further search well into next year shows the same change: all seats in rows 17 - 23 (on the 77W) fully occupied which is wildly improbable.