What always niggles me about this apocryphal anecdote is that no German was flying Fokkers in WW2. Fokker was a Dutch company which started out in Germany before WW1, when it supplied machines like the peerless triplane of Red Baron fame for the German air effort, but had moved back to NL by 1919, and in WW2 only supplied the Dutch air force which was pretty much entirely destroyed on the ground in the Blitzkrieg of 1940.
Bader could have talked about Focke-Wulfs, but that would have spoiled the story.
Its for that reason that Douglas Bader never told that story because he would have known that, which is why its actually credited to Stan Boardman, a man who could not be classed as one of the greatest thinkers, even in Liverpool.