That center pin looks fragile, especially if it's printed along Z axis. How about printing teeth that'd mesh with the belt?

This is indeed a very elegant fastening method.

I wouldn't be surprised if the designer of that CNC machine borrowed it from the popular Prusa MK2 3D printer, which uses a very similar design for its Y-axis belt: https://help.prusa3d.com/guide/2-y-axis-assembly_79992#81120