Thanks for sharing! The Fw190A3 used for the test is a derated one at that time (due to the BMW801D’s own flaw). Engine output was lower to 1520ps at 1.35ata. So the plane didn’t have its best performance. And the test pilot wasn’t very familiar with the Fw190 and was afraid of crashing at low altitude. So he didn’t fly her to the best performance. (In the later test against Typhoon and Spitfire MK12, they did mention it.)
This looks like you follow a myth.
The Brits we not stupid and noted the artificial HP / ata restrictions and tested it with and without it - you find these tests somewhere on this site: