I often wondered about that. They could leave the trim and emblem holes blank and manufacture 67 and 69 since the 68s are closer to 67s, and the 69s require a recessed rectangle, and a different tab for mounting the outboard end of the grille surround.
I often wondered about outer door skins too. No difference in coupe, fastback, and connie on the outer skins all 3 years. Only exception is the window trim moulding holes used on 67/68. Those can be made without the trim holes, and added by the installer if needed.
