By some coincidence (or not), I am the author of all three posts, so I'll try to explain.
In my honest opinion, all three posts represent true questions. The fact that the questions behind them came from a forum thread is irrelevant. The fact that I posted my own answer to them is also irrelevant (self answers are not discouraged on Stack Exchange).
One legitimate critisisim is perhaps the lacks of enough details in the posts. The questions you linked to all have a positive total vote score, so I guess other site users didn't feel these details are missing. In any case, closing such questions is not the right response, but rather we should ask for the missing details (I'll be happy to fill in whatever details you think are missing).
Another possible critisim is that you think these questions are not real questions. We have the close vote process for that, you're free to vote to close any of them, and discuss individually why you believe they are not questions, or just not a good fit for this format.
I think that just because a question is hard, it doesn't mean it's not useful. For example this question has no simple answer at this point, but an answer can be derived at using game theoretical and economic principles. It is not, in my book, a speculative question (perhaps some rephrasing can improve it, but look at the core, not the specific wording, and edit if you can improve it).