I've been using a treadmill desk for the past 8 years and have a stool that I switch between. I'm constantly moving, and the standing desk encourages even more activity throughout the day.
Nurses, who are on their feet for much of the day, tend to live longer than office workers who spend most of their time sitting.
https://www.asrn.org/journal-nursing-today/291-nurses-at-ris...
You can easily see the difference of walking through a city that you visit for a day, versus standing still for 3 hours in a concert hall.
It's like for the risk of thrombosis when you take an airplane, just standing regularly will not help that much. It is the body movement of walking that will enable blood circulation in the body.
I used to alternate between standing and lying on the floor in various yoga poses, pigeon was a common one (I worked from home), but once I got back to working in an office about 14 years ago, it was all standing all the time.
Of course, I sit when I'm in meetings, but that's probably only an hour or so a day. I sit at lunch, and I'll regularly take an afternoon break where I'll sit for 30 minutes or so.
My setup (which is just a solid core door on top of a generic motorized frame) is nice because I can press a button and rapidly change to a different position. The main benefit is that a motorized desk setup, combined with an adjustable VESA monitor arm, and an adjustable drafting stool, provides a tailored ergonomic position whether I'm sitting or standing. Wrists, elbows, back, neck, and eyes are all in a stress-free position.
I really don't see the problem here.
It's also clear that many humans cope well with workdays entirely on their feet: laborers, restaurant workers, store clerks. But many of these jobs and roles feature a lot of good exercise: at least there's walking around, lifting, moving objects. So it is natural to assume that these sorts of workers get plenty of exercise on the job, and they can relax during their time off, without needing a lot of gym memberships or home equipment.
Now we come to standing desks: so you're on your feet for the workday and you may have a better ergonomic stance. You won't get hemorrhoids or DVT or numbness, or whatever nasty stuff comes from sitting a lot. But neither are you really moving around! You're just standing there supporting your own bodyweight. If you're overweight, this may prove to be a chore in itself.
So when a standing-desk professional finishes work, logic indicates that they'll need to also hit the gym, or swimming pool, or do some sort of real exercise, because they were essentially stationary. Yet, they've been on their feet all day! Aren't they fatigued?
According to this study using a standing desk without moving will increase your chance of developing DVT over sitting.
Your body will do what you train it to do, overall. YMMV!