I don't know what question this Vik Khanna is trying to answer, but if you put that article in this article's context it seems as if you are assuming there is a dichotomy between (standing work + no exercise) and (sitting work + exercise). I.e. it appears you are saying one cannot exercise along with standing work. Which is obviously incorrect. This statement from the article you quote is also highly misleading :
The metabolic cost of standing is about 50% greater than the metabolic cost of sitting, but in both cases the absolute load is very small so the incremental increase in benefit is infinitesimal
50% higher metabolic cost is huge. Fitness enthusiasts would give their right hand to increase their rest metabolism by 50% - if giving their right hand didn't reduce the rest metabolism that is. Even if workday is considered only of 4 hours - 50% over 4 hours can surely not be called infinitesimal.
It takes much more energy to stand rather than sit. Not only that, the semi-voluntary movements one makes while thinking are much more energy intensive when standing than when sitting. That is because while standing we move much much heavier body parts - e.g. legs+torso, pelvis+torso, whole body on ankle/knee joint etc. While sitting such movements are typically restricted to arm movements, head movements, leg movements not translating to whole body movements because ass is glued to a chair. It is clear which movements consume more energy. And while thinking there is a lot of semi-voluntary body movement going on.
Then there is the consideration of what our ancestors evolved doing. While it is not standing, standing is still much closer to it than sitting on comfy chairs. Invention of chair doesn't go as far back as early man.