>>> But you can not just roll all your own electronics in a year.
Naturally, there must be some scale threshold where this is true, so I don't doubt your experience. And my workplace doesn't make anything as elaborate as a car, or with such stringent reliability specs. But my experience is that hardware is always finished before software.
FWIW in my experience building both, hardware is always finished first because it’s cheaper to change the software later in the cycle. Much like drywallers patching over electrical/plumbing sins, software fills gaps …
I mean the EEs / MEs can certainly turn out a board and housing in under 6 months, certainly on a yearly cycle. Though for the current automakers, they don't have a team for this so it would take them probably 3 iterations to get good enough to actually scale it to a mass market car, and that is if their team has good talent and strong leadership.
Naturally, there must be some scale threshold where this is true, so I don't doubt your experience. And my workplace doesn't make anything as elaborate as a car, or with such stringent reliability specs. But my experience is that hardware is always finished before software.