It’s because people aren’t aware the 2nd dimension, the looseness of the connection between the planes of the blades, where the screw isn’t (and can never be) p

It’s because people aren’t aware the 2nd dimension, the looseness of the connection between the planes of the blades, where the screw isn’t (and can never be) perfectly tight yet still allows the blades to slide. It’s hard to get the idea across in text. Your second comment helped a lot.