I was thinking the same thing about the signage. Lack of buildings is a good indication. Signs stay up till someone pays to have them taken down which can be decades.
I would have pursued the building construction angle. Find a finished picture then use that to determine the stage of construction it was in. From there research construction documents and look for additional photography showing the building during that stage of construction.
Linking the photos together is complete conjecture. The whole thing reminds me of paleontology where a narratives are built around literal bones and filled in with imagination and educated guesses.
