Even if you already had a good idea of how a course was to be structured, it would still make sense to ask the views of other experts (by which I mean the many experienced and wise people on this forum!). Similarly, asking for views on more obscure topics to include would still seem sensible. So I think the original poster’s request was entirely reasonable.
Perhaps if they’d given a bit more detail the initial response would have been better? I think they’ve ended up getting a lot of useful suggestions though.