People are different. For some it really increases productivity and wellbeing. For others the opposite. I'm not surprised it is about the same on average as measured by work output. I've been working 100% remote since 2017 and I'll never willingly change it.
If I need to do 100% remote, because I may have a light cold and don't want to spread it, I feel miserable after two weeks. That being said, I also will never work 100% on-site again, only if I can walk to work, which given my location, will not happen in the near future.