Questions discussing fictional advanced technology are on-topic. So, we have questions asking about phasers in Star Trek, or ZPMs in Stargate. But what about science/technology that isn't decades/centuries removed from our present science? Given that I'm only referring to questions that come from science-fiction and fantasy works, why would these questions be considered off-topic? I ask because I've asked a few such questions (which don't fall under the auspices of physics.SE), and have gotten downvotes and close votes. (Example questions - 1, 2, 3)
Given the scope expansion to fantasy, alternative history, and all forms of speculative fiction (see Is Fantasy in spec for this site? and What is and what isn't considered science fiction?), there's no reason (as an average user) that I would guess anything about near-future to be considered off-topic.
If the science/technology is near-future, then in my opinion, yes (assuming it meets all other criteria, of course).
If the science/technology is current, i.e. it exists already, then it depends what the question is. If the question is "how does technology X, used in book Y, work?" then it seems to me that isn't on-topic, and would be better asked elsewhere (e.g. perhaps on physics.se or sites like that).
However, I think this is a very grey area, because there are questions about current science/technology that I would say are on-topic, like asking if there is a real-world version of science/tech found in particular scifi, or whether the depiction of the science/tech is accurate (this requires knowledge of both the science/tech and scifi).
I think I would personally base my opinion on whether a knowledge of scifi was needed or especially beneficial in answering the question. If not, then it's off-topic. If it is, then it's on-topic (possibly both here, and on a science/tech SE).
For your first example question, I'm not sure (I voted it up, but before I considered this :)). The "How much volume do we have inside our bones that is empty?" part seems off-topic to me, but if you asked a biologist this, perhaps it's a meaningless question outside of the scifi realm? In that case, it would seem on-topic to me.
For the third example question, I voted it down not because of the real-world aspect, but because I can't see how it can possibly be answered (as in the comment). I certainly don't think it's off-topic, it's just not clear to me.
(I can't read your second example question, because I'm avoiding everything about Miracle Day until it's available here).