With /api/leaderboard/by-id/{leaderboardId}/scores You can currently only do searches based on username, and in cases where user has changed their username on Steam but it has not yet updated to Scoresaber this feature can break. With an ID the specific users score could always be found. This is specifically annoying with the frequency BeatSaber users change their username and wanting to update locally cached pp values on recently ranked scores. Additionally, this saves people from having to deal with hassles like in the attached image.
