Vampires appear throughout Stephen King's fictional multiverse. They appear in the novels "'Salem's Lot", "", "", and ""; the short stories "One for the Road", "The Night Flier", "Popsy", and "The Little Sisters of Eluria"; and are mentioned in a number of other stories. Marvel Comics' "The Dark Tower: End-World Almanac" includes a detailed entry on their categorization.
Vampires appear in literature outside of Stephen King's fictional multiverse.
I believe it is definitely correct because vampires show up in Marvel's take on Stephen King's writing and it wouldn't be much of a stretch to imagine Marvel or anyone else using vampires that aren't related to King's vampires, which is also why I think the system might have seen that as difficult.