The ease of spinning off patternless examples expands the design space for protoypes.
Then comes the reduction to practice. That magnetic cycloid drive might be machined out of an old aluminum flywheel and it's bearings. This one is a more difficult fabrication.
1990 Eccentric Cycloidal Power Generator
This is a tiny reduction box that could transmit 100s of horsepower with OEM levels of fabrication.
This is an extremely complex shape, but a five-axis CNC machine could produce it. Else 'lost PLA' castings.