I don't think all of the aircraft in that video are factual.
Depends on the definition of factual, I guess. Does it only include planes that flew? Planes that were built? Planes whose blueprints reached the desktop of Göring or Galland? Planes whose blueprints were done on a medium more dignified than a tablecloth?
Inventing new planes was a favorite pastime for the German industry between 1935 and 1945 - only second to the art of turning down new ideas. For every flying wing design presented for procurement, there would have been a dozen sketches based on a hundred preliminary ideas. And doing cool art on preliminary ideas is a valid pastime, too; case in point, good old
Ships of the Star Fleet.
At a glance, I'd say about 50% of the planes shown here were seriously considered ideas, 25% were alternate takes, and 25% were sketches that had no serious thinking or calculating behind them in the 1940s yet and certainly would not have featured things like weapons hardpoints, cockpit dome details, landing gear or aerials, not until the 21st century artist added those along with the paint jobs and unit markings.
Also, had time been frozen and had 1946 been a repeat of 1944 rather than a year of its own, it would still have been a year or three too early for most of these planes. Or a year or three too late, depending. The ideas were related to specific strategic situations and planned moves in the game of war, and would only have been built if those moves still remained to be played; a war going well for the Nazis would have been just as much a counter-indication for them as the reality of the war going disastrously was.
Timo Saloniemi