This changes overtime IMO. I've worked from home for years now, initially it's a blessing, in-time it can be a curse.
If you WFH and want to be productive you _must_ learn to plan your day and that usually involved some type of discipline.
If I force myself to go to sleep at midnight, I'm up at eight, no matter what (well, except in sleep disrupting circumstances, like drinking alcohol, no matter how few - I don't do that in the middle of the week anymore).
I think the need for alarm clock is actually a symptom that we live in a culture of sleep deprivation.
I know people who have quite irregular "natural" sleeping periods, and furthermore when they sleep 10-12hrs, they feel ill the whole day. They use the alarm clock to ensure a more regular period, and feel better for it.
If I need more sleep, I let my body sleeping more. Most of the time I don't need it.
In fact I use an alarm clock for working in chunks of 50 minutes, resting 10 minutes. Over time I have a very good idea how the timer is doing without looking at it.
> I've worked from home for years now, initially it's a blessing, in-time it can be a curse.
I had the opposite experience. For me working from home was a curse initially. Over time I have made that a blessing learning lots of different techniques and cultivating them.
But as I am working from home, I am getting more sleep too. I am too waking up without alarm. I dont travel to/from work anymore and therefore it is enough to wake up a bit later. I am also more ok going to sleep sooner, because there is more time for own activities not then it used to be.
There are no hard boundaries preventing your routine from changing into less-focused one over time. E.g. you may get away with a Netflix break in the middle of your work day now, because nobody is looking at what you're doing. And maybe you're susceptible to TV shows, and you'll soon find yourself watching TV shows when you should be working, and then trying to catch up with the work in the evenings or just having your conscience cause you distress. That's one example, maybe you're immune to that, but there could easily be others.
Also on my end, I'm stuck at home with my wife and 11 m.o. kid and, while my wife and I have an agreement that between ~10:00 and 18:00 I am in my office working, it's really hard to resist the urge to help with the kid (especially when she starts crying). It's taking an emotional toll on me. It wasn't that big of a problem before the pandemic, even though I've been WFH for the last ~3 years, because my wife would take the kid for a walk, or arrange playdates with her friend (who's also a mother of similarly-aged child and lives in the apartment building next to ours).
So while technically, you can take a short walk (AFAIR 250 meters from home) and can take your pets and kids out for a walk, whether you actually can do it often depends on the specifics of your particular neighborhood.
They didn’t say they slept in or woke up at varying times - you’ve imagined that - they said they woke up without an alarm clock. That could be at 5am sharp every day for all you know!