My grandfather was a navigator in WW2 on B17's and B24's (halfway through the tour they switched from the 17's to the 24's). I would always ask him about those days, and he was very open to chat about it. Anyway, he said rarely did they ever (keep in mind this was his unit, not the whole ETO) fly at low altitudes (12k), but routinely flew at 30k. Now, I know some of the flamers will jump on me, but this was from a guy who was there, flew 4 missions on D-day alone, was shot down at one point, watched the 262's make passes on them (interesting story there in itself), and continued on for 33 years in the Air Force.
There is no question that real-life and in-game are not mimicked exactly. Changing one aspect offsets another however (c'mon, you guys know this), so while there are inconsistencies, there is a general balance going on.
To the original poster, as a squad, we routinely and fairly accurately, figure out what are bombers and such from the radar. Taking the bombers to extreme altitude isnt a problem, thats just smart play. The question I would ask is why don't most planes perform up there too, at least the ones that should be able to? Someone in bombers at 12k in the game, flying into a hotspot, is really asking for trouble. Thats why we run escorts