I was a little miffed that this blog didn't include a link to that particular study, especially with how vague the citation is, so I went and found the original publication[0].

Of note, they have a "Setting the record straight" addendum[1] that includes a couple important quotes:

"Misconception #1: Office workers should now be confused about whether they should sit or stand, and about whether sit/stand stations are a good idea. They shouldn’t be, says Smith. The study’s main finding was about workers who are required to stand for long periods (i.e. five hours or more) throughout their work shift, without opportunities to sit. Extending this to any worker who stands (e.g. an office worker using a sit-stand desk) is not correct. This is because office workers who stand at these types of workstations likely have the option to sit down when they get tired or when they feel pain in their legs and back."

and

"Misconception #2: We no longer have to worry about the negative health effects of prolonged sitting, thanks to this study. Not so fast, says Smith. There was nothing in this study to refute the research on the health consequences of a sedentary lifestyle. Much of that research is about sitting too much throughout the day—at work, while commuting and at home. This study only focused on prolonged sitting and prolonged standing at work.

"And even within the study, another finding about prolonged sitting at work got lost in the coverage. Yes, prolonged standing occupations were linked with twice the risk of heart disease as prolonged sitting jobs. However, prolonged sitting jobs were still linked, among men, with a 40 per cent higher risk of heart disease compared to jobs that involve a mix of standing, sitting and walking."

[0]: https://www.iwh.on.ca/newsletters/at-work/90/standing-too-lo...

[1]: https://www.iwh.on.ca/news/study-on-prolonged-standing-and-h...

I can think of a lot of confounding factors for that. Are they just looking at standing desks, or also at the numerous blue collar and service industry jobs that demand long hours of standing at machines and registers? If it's just the former, then there's the question of what kind of people choose standing desks over sitting desks. Is it people worried about their health but don't take the time to exercise outside of work and think standing will be enough? If the latter applies, then there's facts about the stresses and complications of being less financially secure, such as less access to healthcare, longer working hours, poorer diets.