From my understanding, JIT is a way to shift the expense of an elastic supply chain onto suppliers whereas the manufacturer on top, with the money and influence just says, "I want it now, I don't care how, make it happen, cheap".
The idea of having just enough inventory without a buffer makes sense in a perfect world, but in reality, this doesn't always work.
The chip shortage and fabs prioritizing other customers over auto manufacturers exposed this weakness. But maybe that's what it takes to break down the system, a massive black swan event? Maybe small failures happen all the time.
What do I know though, I've never worked supply chain logistics and have only made it to Yellow Belt.
Just sounds like an idea dreamed up by MBA's IMHO where real world factors don't exist.