I don't doubt any of the above. There have been many British v-twins, including Brough Superior and Vincent. But these days if you try to sell a v-twin in the U.S. and it is not a sport bike, people immediately start screaming "Harley copy" All of the Japanese v-twin cruisers, Victory, and now Indian are all being called Harley copies. Even my 1985 design '02 Vulcan 750, which looks nothing like a Harley, and has a liquid cooled v-twin with no fins, gets called a Harley copy. Out of some 40 bikes, the Vulcan is the only v-twin I have ever owned.
Harley may not have made the first v-twin, and certainly not the only one, but they have such a stranglehold on that design now that almost everybody considers a v-twin to be a Harley copy.
My one and only British bike was a mid '60s Bonneville. One of the things I love most about many British bikes is their vertical engines, single or twin. I always wondered why Norton used forward inclined cylinders. To me that gave it a Japanese bike look. The Suzuki S40 is the only Japanese bike that uses a vertical cylinder, but it still does not look like a British engine.
I have this thing about tradition, and don't really care for change. I bought a RE B5 because it looks almost like a traditional British single, and has a long stroke and heavy flywheel like a traditional British single. Nobody else makes anything like it. It's been around for a long time. I would sure hate to see it "modernized" into something completely different.