The article mentions employees on "furlough" who are "biding their time". I'm not from the UK, but this appears to mean the government is paying much of their wage while they are not working.
Anecdotally (in the U.S.) I know several people who have remained on unemployment as long as they possibly can, despite the fact that their job would've hired them back by now. Technically this is breaking the rules of unemployment benefits, but there are several easy ways around it.
Not that the increased/extended unemployment benefits have been a bad thing. They were quite necessary, especially early on in the pandemic when there was so much uncertainty. Perhaps they're still necessary. But it seems to me that if you allow people not to work and still have money, many people simply won't work. Mystery solved.