How do you know that? your saying Boeings production of B-17s was not affected at all by them building the B-29 instead of B-17s in some plants? I don't buy that. On its face it makes no sense.
You know the B-29 program cost more than the Manhatten Project right?
Btw; Fw 190, Bf 109, He 111, Ju 88, Do 17, Ju87 were all pre war designs. The He 177 flew a month after the war began and was a pre war design as well. So the Luftwaffe also did not care about improvements? fighter production for them also went up from 1942-1944 so they also sinned in not building fancy enough planes to slow production (if that's your theory)...
I just don't get your argument. If they didn't care why build a F4U-4 why not just fly Wildcats until 1945? If they didn't care? Why build the P-51?
You can't possibly compare US ac production after 12-1941 with production pre 12-1941. The USA constructed a gargantuan (you hardly ever get to use that word in a sentence

)war industry after Pearl Harbor production figures were NEVER going to be "slowed down".