Originally Posted by
myperks
so still not conclusive if it’s the PZ that looked back at the fare basis instead of the booking class, but based on this, fare basis is used, which meant half the accruals (receipt says B)
I agree it's not conclusive, but I'm 98%+ sure that it was the PZ. The effect of clearing an upgrade has been consistent for years, and it's always been exactly this -- you fly in PZ and it credits as, in this case, "ZS" -> "S."