I am skeptical about the value of smoke, fired by CS tanks

Ian Paterson has a photo of an A10CS tank with A Squadron, the 3rd RTR, practicing firing smoke. I believe that this tank carried a low velocity 75mm guns, only suitable for firing smoke or HE. I am skeptical that a close support tank with this size gun could fire a useful smoke round. Perhaps I am wrong, and would have welcomed the presence of smoke, if I had been with them, with the 4th Armoured Brigade, in Cyrenaica in late 1941.