I can see how "soluble supports" enable the moving parts to be printed - but how can a scanner see which parts are connected/unconnected, when viewing from one direction? How could a scanner see that an axle is a freely moving rod snug within a cylinder, when that is hidden? An extreme eg: put the part inside a blackbox, and scan the box.

This looks impossible to me (that you'd need to touch up the model manually), but the article said that's just what "old school" guys think...