The sirens were mainly only used in Poland and France, against undefended populations to strike terror into them. In fact some people were brought up on war crimes for terrorizing civilians later on because of that.
I believe by the time the BOB was taking place they were being phased out already and it wouldn't be much of an impact. The performance difference and simply the LOOK of the squared-off canopy are more important IMO. Minor, yes, but it would be nice to see.