I think the answer I will give is "statistical tolerances." Robot assembly is going to be based on things fitting together a certian way.
When I toured the factories in the mid to late 1990s I saw a lot of CAD being used. This changes how things are put together compared to when done on a drafting board.
I often got frustrated when I took the wood shop (Renamed "Industrial Arts") most of the works was making jigs and fixtures. I simply wanted to make the thing. Not spend a bunch of time for what seemed to be make work. I did not have access to machine tools till I could buy them for myself. I then learned one had to spend as much time making the "jigs and fixtures"
Curiously statistics was one of my favorite subjects. Not the human services and financial parts, more of the parts relating to things like how bells and organ pipes make sounds.
I have mentioned before that one of my mentors had a Bechlor[sp] Cam driven automated screw cutting machine. I also made my own pinion cutting machine. Never finished the wheel cutting machine.
Recently I got out some old AI textbooks from when Neural Nets were a hot topic 30 years ago. It is interesting how some of the test cases relate to finding glitches in cam based automation. If only I had made the connection 30 years ago! What is different now is that computing power is 1000s of times more than it was 30 years ago. So these brute force methods are easier to implement. As one researcher told me some 20 or more years ago. AI does not get interesting till one has 2 trillion bytes to work with. I can go to Best Buy and buy a backup drive with that much storage.
The Jaquet Droz dolls that inspired me to learn all this stuff are based on the same cam technology as the Bechlor[sp] machine. Rotating disks that move rods and sliders back and forth. And probably the same statistical mathematics. Jaquet Droz studied under Bernouli, which is a better known name in the US. Probably since hard drives rely on the Bernuli effect to keep the heads from crashing into the platter. (There was even a brand name for a sort of rigid removable drive.) More spinning disks. Babbage used this same tech in his 1830s computer design. Abstractly there is no real difference between the dolls, Babbages computer, and the 2000 year old Antkeythera device. All of which use cam inspired statistics to do robotic like things. Ironically the Antkeythera device is based on a prior 1000 or more years of celestial observation. What they called the clockwork universe. ---
And lead to the creation of clocks and watches. Because these cycles repeat. Some people also think that this type of mathematics can predict stock markets and gold futures. Not to mention tomorrows weather.
Part of it may also be what one of my mentors said. These people had a large network of freinds and family what made the dolls. They were not the work of one or two people.
It really does take a village.
I think I am also relating my ignorance of automobile repair. (another cam driven machine.) Some of my cousins all did self repair and some went into the business and retired well off. They say that modern cars are more computer than car. They had crews of mechanics and location was a factor is their success. So it is more than simply knowing how to do the work.
For the most part I only have one "Modern" CAD designed watch which is the Tissot PR100 with the microgenerator. I never found the desire to save up for a coxial movement or other modern "Designer watch." Swatch and Casio watches expected. I have been trying to find "cheap" high value quartz movements to experiment with. Not alone as these are selling for some real money online. So someone is collecting this material.
Perhaps I a thinking of Swatch and Casio when I think of modern reparbility. I got two more Swatches this week to see if I can dissemble them.
I can not really speak though as to the repairability of the 2500K to 12K valued watches. Such watches are not practice for my feeble skills to contemplated working on. A glass free spring balance only seems like it could be repaired with a statistical robot finding the fault and choosing a matching part.
(apologies for this wall of text. as I said spoken word does not translate well to the written word.) Here is a photograph that says the same thing. It shows Babbage's workshop and is from Charles Dickens'
Little Dorrit which is about the creation of the first computer and the havoc created by the IPO what sold stock to fund it. (and the only contemporary illustration of the difference engine cams. lower left. The calculating towers can be seen in the center shadows.) None of this was seen till the thing was built.
Robots have been around for a Long time ...