The internal struggle I've always had with these types of stories is that I can't tell if it's something the workers are doing of their own volition, or if they are being made to do it. "Peer pressure" is a pretty wide term and can mean different things depending on the situation.
If I'm at a house part and I'm getting ready to leave, but my buds are telling me "oh don't be a wuss the football game is almost over and our team is winning! you can sleep when you're dead! etc!" I would consider that as "peer pressure".
If I'm in the same situation but I see that there's 20 minutes left on the clock and my team is winning and I really want to see them finish the game because I would miss that moment during my 30 minute drive, and decide it's worth it to stay out a little later that night, I wouldn't consider that peer pressure. Even if my buddies aren't shaming me for leaving, and are instead like "okay drive safe, we're gonna stay so we can watch the end of the game".
I think that's what was meant by the person quoted in the OP saying it's a gray area. I can see how you could be on a team working on a specific thing and have a lot of momentum, and feel like if you just stay a LITTLE longer you'll get over that hump and can feel the relief of finishing that task. That's not to say that's a GOOD or HEALTHY work ethic/mindset/whatever but just that it's something that can happen. So if we *ASSume* that the folks at ND are just working long hours because of THAT, then my question is what could/should ND do about it? If workers are working long hours without being told to or shamed about it, should ND do anything about it? If so, should they make people leave? Would some of them complain that they were getting OT for their work and being forced to go home and thus not get extra money they may need? I'm just very fuzzy on all of this and would really like it if devs themselves could clarify what these situations are like. (I have not yet read Schrier's book)
If a company is coercing/forcing/mandating/enforcing their workers to work more than their standard 40 hours I am absolutely not okay with that, and have worked in some environments that crossed that line in some occasions. If a company allows it's workers to basically set their own hours and work as much as they feel they need to get satisfaction in their work, I am okay with that, but worry about some folks not "knowing when to stop" and allowing their health to suffer. In those cases some protections need to be put in place. Maybe incentives for not going over X amount of hours per week? (allowing for SOME overtime but not a lot) When it comes to peer pressure though I don't have enough management experience to know how to tackle it.
EDIT: I also forgot to mention deadlines- I don't think deadlines are more important than the health/sanity of workers. Period. Games get pushed back all the time, it's okay to me as a consumer to play something later if it means those that made the game happen can see their families and not get put on anxiety meds.