It's not about optimism. It is well established in the industry that Tesla's hardware-stack gives them 98% accuracy at the very most. But those voices are drowned by the marketing bravado.
In the case of Musk it has worked out. His lies have earned him a fortune and now he asks Tesla to pay him out with a casual 1 trillion paycheck.
What does ‘accuracy’ mean here?
To correctly assess the state of the world. Since Tesla exclusively uses visual sensors, they are massively limited in how accurate it can ever be… or safe.
But hey, costs are lower that way.