The real problem is that management doesn't like to pay for updates/upgrades/fixes to make the system more stable (tying back to the management/engineering paragraph in the article).
Disclosure: I'm currently on call.
Does this actually exist? It's like an... anti-holiday. Insane.
Only customers who pay a lot for it have true 24/7, most who pay extra have extended support from IIRC 06-22.
If they can't sort it out, support will try as best they can to work around issues as to not disturb us devs until next morning. I've been woken at most once a year.
Most support folks do say it can be a bit stressful at times, on the other hand they also really enjoy the extended weekend so nobody's been keen to change it.
Part of why it's so useful to do a full week at a time, rather than rotate intra-week, is that whoever's on call needs to have a small purse full of token generators for 2-factor logins, and we typically only get one to share. If they don't have the token they can't help our customer.