|My favourite vampires...|
Anyway, who hasn't read, or watched or heard something featuring a vampire (or other folkloric creature/object) and come to a part that made you (or someone else) say "But I thought they couldn't do that/ could only do that if..."? But who says? What makes the version you previously heard/read/watched better or more accurate than this new idea?
I think we notice changes to folklore because usually folklore is something that changes gradually, over time, by consensus. When a writer decides to make a change to something from folklore, we notice and may wonder why they've done that. Is it more convenient for their plot? Does it question or parody something in contemporary society more effectively with that change in place? Are we convinced by their adaptation?
I suppose, ultimately, that last question is the most important. If something about the writing isn't convincing, we're more likely to question the need to mess with established patterns of folklore.