Building the most accurate DIY CNC lathe in the world [video]

It's kind of sad how much knowledge is hidden inside companies.

(I'm assuming something like this was achieved decades ago in certain companies.)

It has. The Moore Special Tool Company makes diamond turning lathes much like this one. But replicating that precision on your own is still an immense achievement.

As Dan Gelbart once said: "Building your own lathe is an admirable ambition. Building one with micron accuracy is a terrible illness which, at my age, has no cure."

It's pretty much whiplash vs software. In software you get access to the source code for a lot of SOTA industrial sofware in almost every field.

In mechanical engineering/machining/etc. you mostly only get access to educational materials simplified to only demonstrate the concepts... plus a scant few sacred tomes.