Are tail-gunners bullet-proof?

[EJGr.Ost_Caspar]

There is a small indicator - some small star-like yellow flash. I'm not 100% sure, but I think, it shows a hit to a pilot/gunner. Its not a sign of inactivity though.

At the moment it is impossible to tell if a gun position still poses a threat or if it is safe to attack a bomber from this direction

Do you think, this would be a realistic feature? To me it sounds arcade.