Originally Posted by
mvoight
I didn't say that. CX determines whether or not you get miles.
What? That's exactly what you said:
The upgraded ticket was re-ticketed into a ticket with a non mileage booking code.
C is a non-mileage booking code on AA. When you upgrade to business with miles or an EVIP, you are re-ticketed in C. Despite this fact, you earn miles on the original fare paid.
Similarly, you don't get mileage for travel on AAnytime rewards despite the fact that they book into F or J or Y.
In other words, there's a lot more going on than what "booking code" is used for your ticket, unlike your originally asserted "logic".