Why are the paths at least 2 mm wide?

A pencil needs about 2 mm to follow a path. Every page is measured: if the narrowest corridors are under 2 mm (for example Extreme mazes on a small trim, or a look that leaves less room), the Ready to publish card says "The narrowest corridors are X mm: a pencil needs 2 mm or more. Choose an easier level or a bigger trim." and Export waits until it is fixed.