Sure, maybe the only thing preventing any innovation was access to a new material, tho I strongly doubt that for the same reasons many paleontologists doubt it - namely that they frequently weren’t even used, the stone flakes chipped off them were used instead, and that near the end of the period they can be found, there were actually some impactful changes to the design, before revolutionary new materials were found. But likewise in Roman times they were limited (both the skill to make it and decent enough quality material to actually work with)

Only a few people in an area would be metal workers skilled enough to do something like this (and who knows, maybe the dumb thing is an apprentice training item, not actually serving any purpose), and they likely wouldn’t be the ones using it if it is for knitting. So perhaps until the design evolved into something so different we don’t recognize them as iterations, the same one was just used because the people doing the metal work weren’t the people using the tool, and didn’t want to have to design a workflow for something new for marginal increases in usefulness. Perhaps it appearing out of nowhere was also an innovation, lasted until the replacement of an entirely different design caught on or something, and abruptly died out because it wasn’t very good.

Frankly I don’t have a dog in this one, and I don’t think it’s actually a knitting implement, I’m just saying a long time period without design change doesn’t necessarily mean anything.