You're right that the original 4 corners are arbitrary. The hole isn't physically present in the actual space. In fact the word "hole" comes from visualizing the space embedded in a higher space, which we know is not necessary and invites misconceptions. So let's call it a discontinuity.
The discontinuity shows up when you try to continuously map the space to the surface of a sphere. You can almost do it, except for one point. Different nearly-continuous maps have a different point of discontinuity -- it's basically your choice when doing the mapping. I think the 4 corners feels like a natural place for the discontinuity when I visualize that mapping -- and scrolling feels like selecting a different mapping -- but indeed it could be any point in the space if you visualize that mapping differently.
The discontinuity shows up when you try to continuously map the space to the surface of a sphere. You can almost do it, except for one point. Different nearly-continuous maps have a different point of discontinuity -- it's basically your choice when doing the mapping. I think the 4 corners feels like a natural place for the discontinuity when I visualize that mapping -- and scrolling feels like selecting a different mapping -- but indeed it could be any point in the space if you visualize that mapping differently.