I guess AC "technically" does has CPU and the requirement is to purchase a Latitude Flight Pass.

Yes, not the same as UA or any other carriers, but it is "Complimentary" upgrade where you don't need to use your eUpgrade credits.

and I don't think you even need to have status, so it is not CPU (Complimentary Premier Upgrades) it is just CU (Complimentary Upgrades)