I've worked at two fairly large companies during the pandemic, and both have publicly stated that their productivity has increased as a result of WFH. I've heard a variety of measures being mentioned such as profitability, hours worked per week, and responsiveness of employees when they are needed outside of normal working hours for production issues - they found people to be much easier to reach when their home office is their office.

It is clear, however that this data was gathered and released by a different part of the company than the ones that make the call on whether or not people will be required to come back in. Ultimately it's as we would expect: executive leadership deciding to pull people back in has little to do with data and more to do with feelings. Despite publishing that data and overwhelming support for full-time WFH, both have begun the process of pulling people back in.