The core point is you can't go smoothly from a driver assist to fully autonomous. They're just completely different from the point of view of the reliability of the software you need. A huge amount of things with driver assist you can write off as 'the driver will take over'. There's not a specific part of you can point to and say 'that's what will stop them', so much as the entire design of the system needs a different level of consideration because it becomes so safety critical, as opposed to safety-enhancing (autonomous driving is probably the most complex safety critical design ever attempted, by at least an order of magnitude. Driver assist is way easier by comparison). It affects the attributes of the sensors, the design of the neural networks interpreting those sensors, the high level design of the decision making of the whole vehicle, the low-level design of the electronics, basically everything.
Tesla hasn't put forward a plan which indicates their full autonomous development is going to be anything other than a continuation of their driver assist work (and it's certainly frequently and incorrectly stated that the state of their driver assist puts them ahead in the race to full autonomy), and if they want to be credible to those familiar with the challenges involved, they need to actually show something more than that.
> you can't go smoothly from a driver assist to fully autonomous
Ok. So Waymo has developed a 100% reliable full self driving system that handles every possible situation. It was never put in a situation in which it would have given back control to a human driver, because that would have meant "going smoothly" to driver assist mode, and we have already said that this is impossible.
I was not referring to the dynamic shift while in use, I was referring to the development process. Regardless, the waymo system does not have a driver assist mode, it's either in control or it isn't (and during development it may be overridden by or automatically fall back to a safety driver, who has a job akin to a driving instructor, something which general requires more qualifications and attentiveness than a driver).
Tesla hasn't put forward a plan which indicates their full autonomous development is going to be anything other than a continuation of their driver assist work (and it's certainly frequently and incorrectly stated that the state of their driver assist puts them ahead in the race to full autonomy), and if they want to be credible to those familiar with the challenges involved, they need to actually show something more than that.