Never really considered that a "commander's periscope" tbh. more like a guy spotting with binoculars outside the hatch. but you can think of it that way if you want.
Well there's no guy outside the hatch.
In reality, 10:1 magnification of the scissors periscope provided better observation of the target area than the binoculars. Moreover, the aiming sights of the StuG were superior to those of the tanks (2.5:1) or AT-guns (3:1). This is one of the reasons that attributed to the combat effectiveness and the higher armour kill rates of the Sturmartillerie.
Recovery of a Sherman that fell into a bomb crater, breaking a tread. Saint-Gilles, Manche, late July 1944.