They still have to track all those changes - NHTSA requires it for recall & safety purposes -- cars & highway gear are highly regulated.
A good example is the company that changed the design of their guard-rail endcaps. They reduced the size by an inch, which allegedly resulted in 5 deaths (court cases are ongoing). They (again, allegedly) failed to test the change, and failed to report the design change to NHTSA and the various state highway departments that specified it's use.
Another example is the ignition switch in GM cars. The engineer changed the design, but did not issue a new part number for it. Externally, same shape & mounting points & connector pinouts. Internally, very different.
So while a design change in a part might be "like for like", it requires a full lifecycle of testing and documentation. And that's expensive, so auto makers try very hard to get their designs correct up front.
I wonder if this is a place where being young hand having lots of automation really helps out. Organizations invariably grow organically, GM had no way of knowing what would be required of them 50 years ago, so the processes are likely weird.
Tesla's processes will be weird in 50 years - if they're even around. but today, I'd imagine that kind of complexity is way way easier to manage if you're aware of it from the start. Rather than getting it right the first time, build the whole organization around coping with those little variations.
OTOH, i have no evidence they actually do that... Just seems possible for Tesla and very hard for GM.
A good example is the company that changed the design of their guard-rail endcaps. They reduced the size by an inch, which allegedly resulted in 5 deaths (court cases are ongoing). They (again, allegedly) failed to test the change, and failed to report the design change to NHTSA and the various state highway departments that specified it's use.
Another example is the ignition switch in GM cars. The engineer changed the design, but did not issue a new part number for it. Externally, same shape & mounting points & connector pinouts. Internally, very different.
So while a design change in a part might be "like for like", it requires a full lifecycle of testing and documentation. And that's expensive, so auto makers try very hard to get their designs correct up front.