It won’t stop anyone buying or importing innocuous machinery parts like 2020 aluminium extrusions or GT2 belts either. There are mature generic 3D printer designs out there that outperforms RepRap i3 bedslingers.

E.g. https://vorondesign.com/voron2.4

I find it quite hard to believe it would be able to detect innocuous, dual-use, off the shelf components spread out over a dozen prints.

Even US export controls can’t prevent that, only delay and cause irritation.