I don't know where I got the info on the Germans using FM and I am checking my books on the subject including the Signal Corp volumes that analyzes everything comm related from before the war until after.  But the Germans did have a coordinated set up, where troops on the ground could talk to an aircraft or tank to direct fire without having the request go to the rear to be relayed, one of the things pointed out as something to be corrected for the US  in the Signal Corp books. A little known fact was that just prior to the war,  the Army studied ARRL procedures and ham ops in action to learn how to relay a message from one point to another, being amazed at how fast and accurate hams were doing it from coast to coast.   I have a complete SCR22 station for the B17F that I have yet to restore, it is a Canadian made copy of the British TR version and to be honest, I have not messed with it at all and just judged from my misinformation I had about it, it was a total British invention with no massive modulator tubes like the 375, it was FM.   Plus it was a popular unit to put on ham band VHF, I think modified for FM.    Guess the real issue was Brit communications on VHF vs all the US on HF in the B17 and others .  I had one contact with a Brit Lancaster radio op from the era that said they had some Lancasters with BC375's installed.  On the B17 crew members could talk over the BC375 and listen to the BC348 selected  by  their individual control box at their station set to 'Liason'  if they had too, but only pilot and copilot could use the Command Set.  A couple WW II radio ops in contact with our B17F project  said they did not do a lot on the BC375 voice wise, mostly CW but rarely to never in a mission, just when they were in non-combat mode.  Even though they carried all the TU's, the TX was set up before a mission, they did not arbitrarily swap out a TU for another band.  There was a red faced TU that had a goniometer in it and was used as a comm jammer, but a rare unit today.  I have only seen one picture of that one.

Charlie in NC