Also this seems to very much be them suffering from the 90/10 problem that some many software projects suffer from: you can do 90% of the work with 10% of the effort but that also means it takes 90% of the work to do the other 10%.

Earlier people from the outside perceived Tesla as being ahead of everybody else on this because they just started before just about everybody else, were riding the easy part of the curve were you're constant delivering improvements because you're just tackling the easy bits, and they were probably even doing a rush job and taking shortcuts to maintain that apperarence of being ahead of the rest because that maintained an appeareance of Tesla as a Tech Stock rather than an Auto Industry Stock, hence with market valuations 10x or 20x higher than they would others which meant sky-high Tesla Stock Prices justified by how "technologically ahead" they were in a "key future technology" - the company was just executing a typical conman strategy of looking like they were making it in the hope that their early-mover status and the increasing investor funding that strategy pulls in would allow them to actually make it before everybody else or at least with a larger installed base, similarly to how Theranos was doing only unlike that company Tesla did just the right balance of deceit and reality to just be on the right side of the Laws for Fraud.

Tech companies absolutelly can get away with doing this during the early and easy parts of the project because for non-experts it looks like they're doing fast progress - which is why Startups nowadays (which is an Era of way more bullshitty and even fraud in the Industry than, say, pre-2000) commonly do things exactly like this - but then they reach the hard part, progress speed naturaly goes down a lot (the project transitions from the 90%-results/10%-work speed to the 10/90% one) plus all the the early shortcuts (a.k.a. Technical Debt) come due to be paid for: "out of control car careening down the hill" meet "concrete wall".

Finally, I wouldn't at all be surprised if they're stuck down a dead-end for the technology which is the wrong way to reach level 4 and have to go back and redo much if not most of that work they did as a rush job to keep impressing investors and ill-informed customers with how "ahead of the pack" the were. Under the leadership of Musk I suspect that they will never be able to reach level 4.