These days, with CNC milling machines becoming less and less expensive, it would be pretty easy to carve a horimono like that dragon entirely automatically, with just some minor post machine clean-up. The hardest part isn't the carving, it's creating the 3D model... and if you have an old one to 3D scan and replicate, there's just some clean-up and translation of the scan to do. CNC machines do for carving what AI does for video - pretty soon you just won't be able to tell the difference without a microscope. But the quality of nihonto has always been in the steel production and forging anyhow, and that, so far, is beyond a computer :-).