Me too, they had a lot of them so most likely they were used for both purposes. They did have a scarcity of radios though so perhaps it was uncommon, there are other ways to do this.

The artillery was a key factor, it sat on the east bank of the Volga and harassed the Germans endlessly there is an instance of a battalion or a large group of German being slaughtered by a bombardment of Katyushi, before they had even fired a shot in the battle.

I sure can't understand the reasoning for leaving the flanks so weak, it can only be due to incompetence.