Is that true? I avoided ever joining startups because I assumed everyone worked 60 hours every week.
As the other reply says, usually you find people doing longer hours in a few selected periods of a startups life. E.g. First MVP, first big client... crunch time!
However, I would say typical early stage startup work is 55 hours/week.
Basically 10 hours day through the week, and a couple hours on the weekend.
The stress is lower because you usually have more cash flow or significant rounds that make the work more enjoyable and you have a better comfort of working overall.