YC startup founders do not work shifts.

1. They talk about doing this a whole lot more than they actually do it

2. "I worked twelve hours today [not including unlimited bathroom breaks, social breaks, snack breaks, drink breaks, YouTube breaks, going on a walk to clear my head breaks]"

3. To the extent that anyone actually does this with any consistency, it's a laughable example of poor self-management and company leadership

4. It's an example of poor self-management and leadership for the same reason it's bad on assembly lines: it produces bad work

5. They're not building safety-critical devices they're putting out onto public roads

Haven't done YC but did Techstars a while back when they were still in the same league, and except on the week before demo day there was pretty much never anyone at the place after 6pm (except for the handful of foreign teams who didn't have anything do to in their life in the US).

Apples to oranges. Tesla manufactures cars with much more liability.