One important thing to keep in mind about the Osborn manuals: These are a collection of reproduced original Ford individual drawings. The drawings were subject to revision, over time, to denote changes in materials and/or processes. Some drawings had multiple revisions over the 67-68 model years, while others were not revised at all. Since these drawings were collected and reproduced well after 1968, it should be expected that they were the final (aka most current) revision available. So if you are looking at something for a Jan 1967 built car, for example, and look at a Ford drawing revised in April 1968 you could be misled depending on the nature of all revisions after Jan 1967.
Also it is important to appreciate that there were various liberties taken at the assembly plants. Those liberties probably could be summed up in two categories - ones that received approval by plant staff, and others that were done by the line workers.
These nuances make it challenging to restore a car correctly, which is precisely why a web site such as this exists.
If you search the posts you will find that I posed this question a few years ago, and there never was a final determination. I suppose that after the discussion above the term "final determination" is probably not appropriate.
What I can offer is that all of the original 67 fastbacks that I've seen are like yours - no blackout paint in this area.
As for water penetration - water was expected to intrude as far as the black fiberglass like box mounted on the inside of the vehicle. The box should be sealed against the body, and water intrusion is drained via a hose down into the rocker.
