MP Willow:
That is kind of the idea i was trying to land here.
I ve seen footage when the defensive fire is very visible when the German fighter was homing in for the kill; in some cases i can even say the interceptor equipped with the guncamera got hit since kind of moderate/violent shaking is detected in the camera, but it was not enough to bring the German down.
Having seen shots where the defensive fire is clearly visible gave me a pattern to go and see those shots i am herein referring to, and in fact no defensive fire is being fired.
The reasons for that? Many. I still have a hard time trying to figure out why. That is why i said the behavior of a number of gunners on the heavies was odd.