I think it’s unintentional. They recycled the scope view from the Type 97 hull gun on the Ha-Go, so you’re not tunneling, you’re looking at the inside of the hull.
You might be right, I hadn’t noticed. It doesn’t seem to happen when it’s the hull gun on the Ha-Go either. I’ll pay attention when I eventually unlock the type 97 lmg
Depends on the scope, most scopes tunnel at high magnification and tunneling occures when you’re not aligned with the center axis of the scope. Another reason for tunneling is when you’re at the wrong distance from it. All scope have eye relief which means that the eye has to be a certain distance from the back lens so that the image fills the entire lens, too far or too close and you get tunneling.
The higher the magnification on your scope the more accentuated the effects of tunneling are when you’re not aligned or at the wrong distance.
Since the scopes in ww2 were usually around 4x, with the exception of the Unertl scope that was 8x (and i think there was also a 12x version), and they didn’t had variable magnification, the main reason for tunneling would be misalingment with it’s axis (when you get the side shadow).
They definitely should make it so that the part of the screen that’s not the scope lens stays un-magnified - very few games do this, and it’s a nice realistic feature.