This is a technique to take conventional items like nuts and washers and show how by using a Concept Laser Mlab cusing machine, you can 3D print a complex structure on top. This showcases 2 things only 3D print the part that is needed, and using different materials. It also allows you to see that certain structures can be built without any supports, and see the level of fine detail which can be achieved.
Re Building a cylinder head requires applying assembly lube in specific areas to ensure there is no dry parts.