Not sure that I understand the Atlanta angle. It is still a three zone trip.
Because ATL is a border city, it is considered both in the eastern zone and midwest zone. (It doesn't matter that you have to travel thru the eastern zone to get there - thus the loophole!) So from SPK or SEA, you start in the western zone and end in the midwest zone - thus it is only 2 zones! If you start in WPT (another border city), from WPT (where you start in the midwest zone) to ATL (where you end in the midwest zone) would be only a 1 zone award!
But being that you have to board 1 or more trains on a blackout date, you couldn't do it anyway!