If I were to guess why the extra holes were there I would say they could not find the correct mounting clips and used screws to hold the trim piece. If you find the trim strip has holes that would confirm it.
Think you'll find that the strip was originally retained to the trap door with screws. The large hole usage and clips, I think you'll find, is found on 67's
The 67 fastback trim sure looked neater without the screws and holes
Example from one of the unrestored picture threads