I work in a manufacturing company (not cars) and if I tried to explain to someone how we plan our production it would be impossible because it depends on so many factors. The idea that they would be able to explain their process to us, in a few sentences, even if they wanted to is pretty naïve. It probably depends on such a multitude of factors. I imagine those waiting long periods of time could of been waiting for multiple different parts at different times. IE they don't start production because they are waiting on paint. But they are not going to hold the rest of the parts instead of getting another truck out the door, so when the paint comes in they know that if they build the truck it will be waiting for center console, then the machine used to make the longer bed goes down for a week, then when its back up they are out of the components to make a reclining rear seat... All parts must be in at the same time, then there is likely a batching element, and a multitude of other factors.... All dependent on having 1000's of parts available at the same time during a global supply chain catastrophe where they cannot trust the lead times given by their suppliers and parts are constantly stuck in transit. Then there are likely tons of exceptions where certain orders are prioritized for a multitude of different reasons from fixing previous errors all the way to politics, revenue goals, dealer inventories, etc