Actually I think you're both off.
As far as I can tell the last window ENDS 1/2 hour before the park closes.
IE. If the park closes at 10, the last window is 8:30 to 9:30. This leaves them 1/2 an hour before closing to clear out the last of the fastpass queue (and get a head start on clearing out the last of the regular queue without last minute fastpass admissions slowing it down).
For instance, I booked fastpasses for the short window between 4pm and 7pm before my not so scary and very merry tickets this year. The park closed at 7 before both parties, and the latest fast pass I could book both days was the 5:30 to 6:30 window. (Had to book 3:30-4:30, 4:30-5:30 & 5:30-6:30 on both occasions.)