I think that they’re stupid as fuck and don’t really operate on rules. it’s like The Evil Dead. Sam Raimi has said that in order for it to be scary there has to be one rule: The Deadites (Or zombies) can come at any time, for any reason. Sometimes a person turns into one because they fall in mud (WHAT??) sometimes they turn because they are bitten, yet when ash is bitten only his hand turns. At one point a girl gets stabbed with a pencil and turns. I think the same goes for the vampires in FDTD. They have no rules, because they wanted it to be scary and/or they wanted it to resemble the crappy horror movies of the 80’s.
