Could be. All I know is what Matt wrote on his drawing.
It seems to me that phasers fire often hits it's target without being directly pointed at it. Help me out it I'm misremembering something, but do our heroes ever
miss a phaser shot? Seems to me that the weapon has it's own targeting computer that makes sure the beam hits a valid target, usually a person. Maybe it hits the person closest to the center of the axis of the phaser so aiming when there are multiple targets is important. The sight screen could be how you'd select a target (or at least see what the phaser thinks is the target) before you hit the firing stud.
There's no reason we can't assume it's just a mode select display, but I like it being a scope for several reasons. First, it complies with Jefferies design. Second, the forward end of the phaser I has a clear window for the sight which corresponds to another clear window on the pistol body which suggests that a through-line is indeed there, which makes sense in a LOS way of thinking.