They didn't say the location contained them, just that it was associated with them, which obviously it is for at least some fraction of the population.
While we're pedanting, I believe the location is where his death scene was filmed; he was buried somewhere else.
Because beaches are terrible places for graves, one good storm, the beach shifts and you've got to bury them all over again.
maybe go back and watch the movie; it shows Harry digging his grave slightly above the high tide line, same location.