TL;DR we're nowhere close to exploiting the full potential of nanoscale mechanical systems.
Since I just now learned about that link, I haven't read the book to know, but I have always been interested in finding out if the ability to create smaller and smaller machines is possible by having an outer machine which manufactures an inner, smaller, copy of itself, apply the process of induction, define the termination criteria, ..., profit!
Or, maybe I'm thinking about the problem all wrong -- it's not the actual construction machinery that's the problem, it's providing the input materials to each step (gears, levers, fasteners, wiring(?), etc)
There's a Factorio-clone hiding in this problem ...
So you end up having to learn an experiment at a more and more difficult to access scale to figure out how to make something actually work.
That’s real life anyway.
Many cell phones now have sensors that are mems-based, built using lithography (accelerometers being the best example). In many senses, we've started to achieve the goals of the book.
You might also enjoy Diamond Age.
I'm about 175 pages into that PDF and am now sorry that I drew attention to it. I was beguiled by the name recognition and the snazzy title, but I find the text filled with hand-wavery and aspirational thinking, and it also seems to focus a lot more on DNA than I would have expected
I also find even their aspirations suspicious that any such machinery could ever possibly exist to just tweezer atoms around like marbles and voila gold from lead!
We can already push atoms around with macro-scale actuators that have nano-scale accuracy (which is clumsy, to be sure), and there is little doubt that the hardware to do so will get smaller and more capable over time.