Instead of everything opening up at the start of the process, then quickly filling up, like the East and West seats, the endzone seats are reserved for the previous season ticket holder until they choose to buy or not. I am not sure how long they stay reserved after your allotted time, but they open or not in seemingly random fashion.

The day before my time, it looked like nothing better was open, so we planned to just get our same 11 seats split between rows 14 and 6.
When we went in for our time, a block of 12 (6 on each row) opened up on rows 13 and 14, closer to the aisle. Those were not open before. We took those instead, so whoever was after us suddenly had the option of some great seats on rows 14 or 6.
If we waited, maybe something even better opened up, but maybe not... Needing a large group of tickets limits the options.
Anyway... Hopefully that makes more sense.