CX has a way of tracking revenue flown against name and is not based on your MPC status.

In the 2000s, I had flown on CX in J/F on more than a few times but all my miles were credited to AA. But yet one day the ISM commented that I was one of their CIP because of my flight patterns. The ISM said that there is a way CX knows who pays and who flies for free based on the name. I have been OPup'd to F where I have usually been the only passenger and the J cabin is not even full.

Its not impossible. SQ's reservation system for example tracks name and appends KF/PPS numbers automatically once the transaction ends where no PPS/FQTV info is added in the beginning. CX uses a similar formula I think.