I'm very familiar with Demings (I wouldn't say he saved the US car industry. He was ignored here. It wasn't until Japan took his works and almost destroyed the US industry that he was taken seriously).

But that brings ups up a specific example of where Tesla has struggled. They used to keep HUGE backstocks of excess inventory (I believe they have since tamed this) which is a classic manufacturing mistake. So if you have any production mistakes or improvements in the part, you have to scrap or just cycle through the entire inventory until the improvements show up in the car.

This is why Just-In-Time is such an important concept in manufacturing. You can iterate constantly. Meanwhile, Tesla would crank out huge batches of identical fenders and doors and mirrors to maximise efficiency (economies of scale) but then struggle with part fits and panel gaps.

Tesla has since dealt with a lot of this when they went through their production hell period. But a lot of what they had to do was re-learn things like Lean Manufacturing and JIT.