On one hand, a fictional work makes no claim to tell the truth about anything. Any facts presented are merely verisimilitude, and authors are considered free to mix fact and fiction in whatever way helps them to tell their story. Therefore a statement made in fiction should not really be considered a proper claim. On the other hand many people may read such a statement and believe it, so finding out the truth is worthwhile.
How should we treat such statements? Clearly a statement about in-universe matters such as Dalek biology is off topic, but how should we deal with statements where the author seems to be showing their research? (warning: TV Tropes link).