Tires with different codes are different from each other. I can tell you that the Michelin PS2s (N2) for my 911 are different from the the PS2s made specifically for Cadillac ( same size). The PS2s for the 911 have a wider tread and start out with a slightly shorter tread. I learned this when researching replacements when these were in short supply.
It is not a gimmick. Tires are often optimized for different car models. Further, if a tire model ( non car model spec) is sold through Costco or some other large retail outlet, it is not exactly the same as the tire sold at a dealer or smaller tire centers.
Yes, you can use the same model tire with a different or non-existent car code but they might not give the same mpg ( or range) or sound the same or handle the same or ride the same.