According to the docs, the pre-user registration action trigger only runs for Database and Passwordless users, not for social connection users such as Spotify.
You can instead use a Post Login Action and check if it is the first login:
exports.onExecutePostLogin = async (event, api) => {
if (event.stats.logins_count === 1) {
api.user.setAppMetadata('vip', true);
}
};