Sorry, just my notes. There was a French man, name started with an 'L', he lived in Japan before the war. In '45 he was brought in by the USA as a translator for the PTHINT's, he was the one who started this error.
I spotted it because he correctly listed the A6M2 as 302 kts and the N1K1-J he listed at 363kts. Later in his appendices he adjusted these speeds to mph, presumably because the Americans asked him to, and he listed the A6M2 at 332mph and the N1K1-j at 363mph.
I think it was a simple error by an overworked man but no questioned it for 20 years and by then it was set in stone.
One of the easiest things to do is read up about the N1K1-j, it was regarded by everyone as a very clean, aerodynamic design. It was quite light by American standards, and was powered by a 1990hp engine. Then compare it's power to weight to any American or British fighter.
Then think about the speeds these compared aircraft reach. You will see the discrepancy.
You cannot get this info from the Library of Congress anymore because everything has been re-classified by my insane, paranoid government which thinks the flow of information is bad. If i had known we were going to reclassify this stuff i would have bought a hand scanner but i just took notes.