It really just depends on whether people can figure out the answers. These are not quiz questions, after all; the goal is to get people answers to their queries, not to prove anything about how clever or knowledgeable the answerers are. If people somebody can figure out the answer just from a single-sentence blurb, then that's all that is really needed. Obviously, well-known works are going to be easier to identify. Of the five on your list, I was able to get the first two without even a second thought.
Moreover, while there are guidelines for what makes a good story identification question, we ultimately cannot control how much information a questioner has about the work the are looking for. Some works are only very vaguely remembered, and some questions come to us second hand. It is not always possible to add more detail about when a book was read, or what the style of animation of a film was. The "best" questions are those that provide the most information, because they are the easiest to answer; and because they are will be the most useful to other people looking for the same work in the future. However, that does not mean that questions with less information are unanswerable; they are just harder.
Sometimes, a very minimal question will get a prompt answer, and the original asker will agree that the right work has been found. In cases like this, it might be advantageous to edit more information into the question and/or answer after it has been confirmed. However, by the most elementary indicator, the question has been successful: An answer was found. Thus, ipso facto, the question was not too broad or vague to be answerable.