I class on AeroMexico used to be an award bucket, but now is discount J. I think the mileage earning rules have never been updated to reflect this.

This isn't unusual given the state of communication between SkyTeam partners. A similar situation happened with AZ when they added E class, which is one notch below full J. For several years, DLs earning charts didn't include E, so you'd get 0% credit for it in terms of RDM and MQM. Imagine paying $10k for an E class ticket and being told you wouldn't get any credit for it.