As IluvSQ mentioned, United includes all eligible AQM flights - based on fare on the AP site.
https://www4.aeroplan.com/earn_miles...Partner=United
So let's say you went 2000 roundtrip on a Z class; 2000 base fare AQMs (100%) + 1000 COS AQMS (50% of base) + 2000 bonus non-AQM AE points (100% of base)
On the return, S only earns 50% mileage based on the AP site; 1000 base fare AQMs (50%) + 1000 bonus non-AQM AE points (100% of base)
One other item to note is that when a new year starts, occasionally there has been a delay in the 100% mileage bonus - depending on your previous / new status, as you choose your options.