Boundaries are messy. Even in startups it's hard to say "this is my time" and this is "company time" especially with remote work becoming more common.

I've always taken the approach of not apologizing when I'm "not available" on days I requested off or when it's late at night. If I have significant equity, I'll care. But if I'm just salaried or at a BigCorp you can fuck off if it's after 10pm. I never understood why I knew co-workers at Amazon who would pull all nighters on weekends to "fix issues". Basically, I don't want to work for a company that rewards that kind of thing - time is worth too much. Hustle is worth it when you know how much skin you have in the game and can benefit from it more than your employer.