You know what I mean smart ass!
Now having said that, we can forget about all the "drawing board" just a dream aircraft. They did not see combat? What is good for aircraft that were flown back in the US or Canada or any other country is good for all aircraft.
Point being, if it was built during WW2, it is a WW2 aircraft and if it is a military aircraft it can be classified as a war bird.
I've just always seen the description 'Warbird' as that of an a/c which saw combat during WW2, whilst the others were just WW2 aircraft, designs or prototypes. But I see the logic in your way of thinking as-well, with any military bird being a warbird, makes sense. Just goes to prove that every man has a different way of looking at things at times