Maybe it can be modified to something like:

“Any headline that ends in a question mark can be answered by yes or no, whichever seems the most obvious.”

That’s just a 3d perspective along the Z axis

Cutting a sandwich ‘along the middle’ is still considered a vertical cut, just along a different plane. Same as cutting corner to corner. Vertical but on a plane that isn’t orthogonal to the major XYZ axes.