So, this guy isn't doing much good, with 2.5-3 miles walking a day at 1.8 miles/hour (1h25m to 1h40m of walking)?

I expect that, in 10 years or so, we will SE more nuanced publications about the health effects of sitting less.

Looking at chimps in nature, I expect the optimum will be something where you don't sit in the same position for hours at an end, but hobble a few meters every half hour or so and grab some fruit or groom a colleague (the latter would require significant changes in workplace ethics and law)

"hobble a few meters every half hour or so"

I get up every hour almost without fail, and walk all the way across the building to get a drink, or bathroom break, or any excuse, sometimes I do nothing at all. Often I walk to a different floor. This was on dr advice a long time ago WRT back probs and general health. I'm a heck of a lot more productive in the 10 minutes after I get back than the 10 minutes before, so its almost certainly a substantial net gain to my employer.

I do the same daily mileage as the author but compressed into my lunch hour, in addition to the above, weather permitting. I'd be interested to see shoe wear stats. When I slack off in the depths of winter or the peak of summer I can see my shoe soles not wear when I don't do a couple miles of pavement at lunch hour.

Its also interesting to look at financially, I can only get a couple hundred miles out of a pair of shoes, and I need to buy decent walking shoes not cheap junk solely based on appearance. I would guess shoe wear on a rubber belt is very low compared to concrete... then again I don't pay for whatever wear I cause to the concrete sidewalk and someone is paying for his treadmill wear directly or indirectly.

When I worked in a suburban office building I walked the nature trails and shoe wear on shredded bark was approximately zero, and it was more emotionally satisfying than dodging panhandlers in the city.

Related to above I tried wearing trail hiking boots and the wear was high on pavement. Lunch hour walks would probably be a good strategy for breaking in new boots, but it doesn't work long term for exercise.

It was an interesting article although there's plenty of space for further study.

Similarly, simply standing has been shown (by some studies, though I don't know how far these are through the peer review and such processes) to be beneficial. This is why some use standing desks. The differences (to posture, circulation, a few more calories burned, & so on) may be small - but a small positive is still a positive.