I'm not so sure about this. I was working in a remote "full-stack" (but really 90% front-end role) for 14 months from the start of January 2021 to the end of February 2022. I tracked my hours religiously the entire time I was employed there (not required, but just for my own sake). I had a spreadsheet containing the date, start/end times (rounded to the nearest quarter on an hour), task name, and notes.
When I left the company, my team lead thought I was one of the hardest working people he had ever worked with. He thought I had to be working 60-hour weeks to be doing what I was doing. I showed him the spreadsheet and calculated the average hours worked per week - came out somewhere between 38~39 hours.
My role wasn't a senior one so, for the most part, the vast majority hours were spent coding, but of course some was spent in meetings as well. But these were all real hours of real time spent working. It was all very doable and not useless time spent futzing around (I would also stop tracking my time for any break I took - no exceptions).
Granted, I think being the type of person that acclimates well to remote work made this all doable. I would not have been this productive in office.