WoW - Do player id's change when they faction or server transfer?


I’m building a tool around the pvp leaderboard api and noticed that some players were duplicated after they faction changed. Closer look it appears they have a new id. Is this normal? Id’s ideally should never change.

Is there something else I should be looking at that never changes to better track the player?

update: Just 2 different players with the same ID. Lovely.