The article doesn't say whether the tracked workers are hourly or salaried, but it makes a big difference. The article also doesn't touch on total hours worked

The article doesn't say whether the tracked workers are hourly or salaried, but it makes a big difference. The article also doesn't touch on total hours worked during the week, but that makes a big difference, too. If hourly workers are logging off early on Friday, it could be because they've already put in enough hours earlier in the week that they'd be veering into overtime territory if they were to work late on Friday, and so it's their employer, rather than them, who is making the call. But if it's salaried workers who are logging off early on Friday, it's likely because they recognize that working late on a Friday isn't actually going to accomplish much (especially if others are leaving early, too) and so it's not worth putting in the extra time.