But how do you define “productive”?

Studies that I’ve seen have seen both an increase in time to perform work and a decrease in quality of work.

You are noting that you take more time, but you work that additional time. Not everyone does that.

Increased employee happiness/retention and reduced office rent may be good reasons why to pick full remote over the increased productivity of the office, but the idea that people are more productive at home isn’t proving itself to be true.