Originally Posted by
demue
Upgrades come out of a different "bucket / pool" (fare buckets) than full saver redemptions who also come out of a different pool than advantage redemptions. The info you got is correct.
Now how much sense it makes to offer full outright redemption space but not upgrade space at the same time for the same flight is an entirely separate conversation.
Not the same situation, but there is one more wrinkle. One only needs to find advantage redemption space in order to use a PPS upgrade certificate.