I do not understand why you would be due compensation. You booked a Saver fare and chose an allowed seat in the last 3 rows of the plane. You did not pay anything to be able to choose that seat. And it is not guaranteed. If you wanted a window seat, and there was none left in the Saver section, you could have paid a fee to sit in the Premium section—— for the flight I just looked at ( SEA to SFO) that fee is $43, $20 less than the fee for someone in the Main cabin to upgrade to the Premium section. Maybe it goes up as it gets closer to the date? I don’t see how it could be $160. In any case, there appears to be no option for someone with a Saver fare to pay a fee to sit in the Main cabin, only the Premium.