I was there for 10 years and I don't recall any mass layoffs. The article says this is about reducing expenses. Note that the article doesn't say if the layoffs were in Los Gatos or in the Hollywood office, or both.
The keeper test is mostly about helping managers be effective when they need to remove someone from their team. It eliminates the bureaucratic red tape that most companies have for firing someone. Managers at Netflix are still expected to give feedback to everyone about their performance and if there is a problem, give someone an opportunity to improve. No one should be surprised if they are let go for performance reasons.
The difference is that at Netflix someone who isn't keeping up will not be subjected to a 1+ year long process driven by HR before they are eventually fired. Instead they will be given specific time by their manager and if the problem isn't fixed fairly quickly, the manager can decide to let them go.
Most people have been on a team where there was somebody who was constantly slowing everything down or causing other problems. If you're a manager, you know that those people end up taking a huge portion of your time. At Netflix, managers are effective at removing those people.