OKAY - Riddle me this, Batman...

IF substantially different parts (e.g., bumpers) define one model as distinct from another model, AND we can't put SOME of the parts from one model on another model without creating a model that never existed, THEN why even have the update/backdate rule that defines "assemblies" as the basis for updating/backdating...?

The only allowance for updating/backdating consistent with the assumptions being presented here would require updating/backdating ANY AND ALL parts/assemblies that are different, or none at all. And THAT wouldn't have been legal under the VIN rule restriction, since the VIN defines a model because it's year-specific.

Hmmm?

Kirk (who's increasingly baffled by the great inconsistencies here, between what he thought he understood and what is being presented here)