If the regulatory burden for starting a new car company was that high, you would have never seen Tesla, which means you would never see any pressure on the big guys to go all electric. So you need to balance regulation with innovation.
All of that information is required knowledge for the business to operate and production to continue. You can't make something if you don't even know what materials you need to make it, nor if you don't know how to put it together.
In the case of extremely low production with hand-fitting the documented process may vary some from the actual process but it shouldn't be so significant that one product does not even resemble another.
Besides many countries do require automobile mass market vendors to offer spare parts and docs on FRAND conditions to "unconnected" repair shops already.