For the past 10 years or so I've been doing "hybrid WFH" where I negotiate 3 days max in-office (when I'm working somewhere with an office close to where I live) and I always get it agreed upon in my employment contract. My guess (and bias) would be that companies that would pull this switcheroo on employees would be larger orgs with faceless HR machinery and most wherewithal to dominate their employees (ie Amazon)