I kept a log in almost real-time (e.g., after a meeting or a stint of work, I'd enter in the time).

I agree that my conclusion that working from home was more productive is not as strong as it should be. Because I was timing myself, I tried as hard as I could to stay focused while the stopwatch was running. So aside from meetings and teaching, I don't think my productivity varied minute by minute between WFH and office.

If I had a better way of measuring productivity, then I'd use that. For what it's worth, most of my writing time was at home.