Building the most accurate DIY CNC lathe in the world [video]

I recently saw another video about a high accuracy 3d positioning stage. The differences and similarities were very interesting. For instance, both used rigid rods with ball joints for accuracy, but wildly different encoders and testing methods.

https://youtu.be/MgQbPdiuUTw?si=5r0DVsxVT1owyKk6