That's basically all it was. Appearance packages often didn't matter on the build line at that point. It would be good to confirm the details in other ways just as others have to when not stamped on there. But as you probably know, VN seemed to not do this, Norwood often did, but still not always and in later years probably less than before. I'm not sure what you call the Formula kit but check the VIN in the dash to confirm Formula, but it won't tell if a W50. For 1980 it should still be 2U87...etc.
Having said that, it always seemed redundant that they'd stamp bucket seats since they all were, and then not bother with options less common!