Are these types of questions appropriate?
- In which syllabus in the U.S. Can the Poisson Distribution Formula be found?
- Why is technique $A$ not in Qualification $B$?
And similar questions?
For the first example question, it sounds as though you are asking others to search the internet for you. That doesn't seem particularly interesting, so (for instance) I wouldn't answer such a question. For the second question, it sounds like you're asking us why someone elsewhere made some subjective decision. There generically isn't a best way to create a syllabus, so I don't expect such a question to have a good answer.
There may be questions related to syllabi that are appropriate on some of the StackExchange sites, though.
For example, you could ask for resources to learn or study about topics included on a syllabus here. Of course, usually a syllabus will also include some underlying textbooks or sets of notes, so this isn't yet a good question. But suppose you saw a syllabus for a first modern number theory class that references Ireland&Rosen's introductory book, and you tried to learn about the Euclidean Algorithm from this book... but didn't understand. Now this leads to a good question for this site: an actionable, precise question about a topic that you're trying to understand.
From an educator's perspective, it may be appropriate to ask about the content of syllabi. This general topic sounds like it would be a better fit for MathEducators.SE (which I'm not particularly familiar with, but I suspect questions of this sort arise there).
Your second question sounds either very precise or very subjective, based on what A and B are. And typically I suspect that a good approach would be to ask the creator of the qualification and just learn why some technique is or is not included. But I would expect the answer to be This is how it's been for a long time.