A few years back it was chic for the NYTimes to call out people who sit down too much - it would cause all kinds of things from diabetes to instant death - okay, I exaggerate - slightly. Apparently it is still chic at the NYTimes!
Some of us might be able to stand at our office desk but if you work in some occupation where it is difficult to stand and work such as being a computer programmer, or drive, it makes life difficult to work and stand. There are jobs you have to do sitting down. Although some of us can use exercise balls or other ergonomic seating to alleviate some of the damage to the lower spine. This might help for some of us who can use other options, but you can't pull the seat out of a taxi and use an exercise ball instead.
What I have thought would be better is to be able to squat instead. In a lot of cultures and in many non-western civilizations, and native cultures, they squat rather than sit. In western culture we do NOT squat, it is uncivilized, which I think is the problem. I've been in Asian and squatted and it was felt far better for the hips, pelvis and over-all spine health than sitting ever has.
The problem with squatting is we can lose the ability to do so if our spine, hips and pelvis become too damaged.
Standing is fine but not a complete solution, in my opinion. Unless your spine, hips and pelvis is damaged, then you have to stand.
I don't have anything to prove that squatting is better for long term work other than my own experience. I don't know how squatting compares to sitting on an exercise ball.