When I read the question, "If the architecture of an 18-hole course isn’t interesting at 6,400 yards, there is no chance it will be more interesting at 7,400 yards", I wasn't compelled to think about it in terms of my length, or anyone else and how far they hit the ball. The question is about whether or not the architecture of a course is interesting, which has little to do with length and everything to do with the merits of what is on the ground.
As Tommy notes about his home courses, the architecture is interesting from multiple tees due to the fact that "the shots on and around the greens are what make the courses fascinating".
I really don't believe anyone thinks that a dozen and a half tree lined runways of various lengths that end at pancakes flanked by sand is somehow going to be much better if 1,000 yds. is added to the overall length - at least I hope they don't.