Haha it's so ridiculous that these articles never take into consideration that people in the office don't have a lot of productive time.
I had the same, I would have a somewhat easy first hour, then spend 2 to 3 hours really focusing and then I'd basically be done for the day and would spend some time idling after lunch until I deemed it was an appropriate time to leave and "work some more from home".
My best year billability wise was the first year of the covid lockdowns, I managed to generate something like 25% more just because of being able to work from home and cutting back on the travel time to customers and being able to multi-task occasionally when I had a quiet day for a customer. I'm glad I live in the Netherlands, hybrid/remote working seems like it'll remain over here at least.