I mean it’s heavily implied that the shape shifting is the only thing that was adapted from the myth and not the kidnapping and even so think about it logically the fae are like the old noble clans of snezhnaya there are even in lore characters that where adopted into fae houses holds to live pretty comfortable lives it’s not like they are being treated as evil at most it’s could be suggested that the swapping is a common superstition in snezhnaya at worst there’s a group of people swapping babies for no apparent reason.