[Franek Grabowski]

Jon
I suppose in Ardennes Germans simply feared of being detected and it was the main reason to atack in poor weather to achieve maximum surprise.
Bill
Personally, I am very sceptical to any Galland's quotes. That is one thing. Another is, that no doubt Mustang won the airwar for Allies due to its superior range (may we call it range in terms of 1940s?) .
We also should be very cautious in regard of what was claimed and what was actually achieved. I am afraid that this was never a subject of serious research, although perhaps there is something in various USAF studies.
Finally, Normandy. A friendly fighter pilot who flew several dive bombing sorties, noted that Mustang accelerated too fast to be effective bomber. Other aircraft were not much better, so we may say that in general bombs were not effective. Rockets were badly inaccurate against ground targets, so only guns remain. Indeed it was most accurate weapon but no aircraft in Normandy had effective guns for ground attack.
On the other hand it must be said that in general aircraft of WWII period were not effective against small, moving military targets, at least in modern terms.
Certainly it was not that hopeless on the other side, as the weapon has been developed. So we should neither overestimate or understimate it.
Best wishes