Ah yes, the Spanish Theory of Value, where management figures maximum value can only be achieved by having workers completely crushed and miserable by an impossible deadline. Of course, this leads to engineers rolling their eyes, giving massively inflated estimates, and eventually moving on to a new company. Tesla is infamous for being way too optimistic in their schedules. Whether it's hopeless optimism or the Spanish Theory at work, I have no idea, but I'm certainly not surprised the factory rework took longer than Tesla was hoping.
Typically, dates are broadcast from somewhere up the chain and even if the folks in the trenches know it's impossible, their safest play is to keep their heads down and let it blow over since being the guy that stands up and says it's not going to happen gets you fired as being "negative", "not committed", or "not a team player". The folks talking to customers are generally relaying the expectations that have been given to them, so they're not intentionally lying though some may know in their gut that the dates they've been told to give aren't likely to be met. Unfortunately, that's how 95% of companies (mal)function, even some of the good ones.
"I love deadlines. I love the wooshing noise they make as they go by." -- Douglas Adams