Isn’t this light emitted by the spot bouncing and hitting the wall next to it? If there is no corner, such bounced light will cover larger and more distant area, so it will have smaller effect on the overall lighting, but a close corner wall will capture significant part of the bounced light.
In fact, I didn’t made that. My company bought that. And I scaled up to match sith Shapespark.
I just set lights and different materials, because materials of pictures of frames are doesn’t divided separately.
But two walls made corner, like coned lego blocks. And they have a same material.