Can you imagine each Tetris shape, one after the other, in some kind of spatial way? Can you "make" the L shaped one sit on its short side then lie down on the long side?
Can't quite play tetris, however - i start to lose track of the pieces once there are like 5-10 of them.
Or mark the edges of a cube into thirds, and cut off each of its corners back to the marks. What does the result look like? Can you mentally rotate this shape around?
If I try to imagine a cube, and then mark the edges into thirds, I cannot imagine what remains when I cut off corners back to the mark. And the cube itself is more of an idea of a cube rather than visual representation.
I cannot mentally rotate the shape as I do not see a shape.
I'm sure it's hard to believe, but trust me, it's hard for me to believe people can visualize in the way people describe.