I agree with your argument that a 1945 German conscipt squad probably should not have Spray Fire capability in ASL game terms. I think the issue is that there are no German units to represent reservists except for the 4-3-6, or when the 4-3-6 represents reservists, it must match reservists for the entire timeframe of the war. German reservists during most of the war probably had the training from their past service to fire at more than one (i.e., 2) hexes, as "Spraying FIre". By 1945 the composition of volksturm units would be very young, hardly trained soldiers. Probably a SSR could indicate no spray fire for 4-3-6s in cases where it might not be warranted, like in all or most of 1945.
To be clear, spraying fire, though it may sound like a lot of bullets, does not necessarily mean a lot of bullets in ASL. It's just that half the squad is self directing its fire (by a squad leader or an assistant squad leader) over a wider area than just a single hex.