I think it's a marketing pipeline for founders. Maybe very early stage employees.
After reading many pg essays, I have this feeling that he's protective of founders. Not just YC founders, or other founders. But possible founders, too. Really the "spirit" of "founder" as it appears to him. (Use "idea" instead of "spirit" if it sounds too woo for you.)
He sometimes sees this spirit as under attack. Some other writer will dogmatically insist on work/life balance. It's probably targeted at the majority of working people who are selling their labor for the wages they need to get by. Personally, I think it's a good message. But there's no specific carve out in the article for founders, so maybe one person out there is a little less foundery than they would be otherwise. This worries pg.
So he writes some sentence like the one that kicked off this comment chain. It's really just "leave founders alone!". The intended effect is that those other writers insist a little less dogmatically, and that people feel enabled to dive into their own projects a bit more.
What the top comment is responding to is the perversion that so often happens. The line gets taken not just as gospel for the founder to live, but to preach. "We're looking for people who believe in work dash life, not work slash life." they say to the software engineer they're expecting to pop tickets off of JIRA for 40% below market wages and options on 0.01% of the company.
A job should absolutely be able to be just a job you perform to generate income if you can do the job, regardless of passion for it. The bar is high enough already for employees trying to climb the employment/career rock face without retired “thought leaders” adding additional constraints.