You can sit at a standing desk. Even if it's not a mechanical one, you can sit in a taller chair. You don't have to stand all day.
You can't stand up at a sitting desk unless you get a Varidesk or something. But then you have a standing desk.
You even say yourself that a standing desk can help with some select problems. What select problems does a sitting desk solve that can't be solved by sitting at a standing desk? If one helps with some problems, and one doesn't, which is the better option?
And let's not downplay the "select" problems that it helps with. Mainly back pain, nerve problems and posture issues. These are not small, trivial problems for a lot of people.