With the number of employees in the company, and they surely talk to each other, it would be impossible to keep any really big negatives a secret. A sufficiently disgruntled employee (say, one who ends up with a lemon) likely wouldn't care about his career with the company.
Why? Timeline goals are arbitrary. It's probably better public relations to promise late and deliver early than to promise early and deliver late, but what really matters are quality and performance. Other companies deliver "on time" (i.e. they're better at accurately assessing how long it will take to bring a car to market) and they deliver cars that are not as safe, don't perform as well, and run on stinky petroleum.
It would be nice to know exactly when I'm going to get my car. But it's far more important to get a safe, reliable car that's fun to drive and does not contribute to global climate change. (Here in the PNW my electricity comes from hydro.)