[1] https://youtu.be/IzH54FpWAP0&t=530
Your clip is about Apple reaching customers for a subscription or hardware, via third parties' marketing channels.
Sign In With Apple is a Single Sign-On service like any other. Something a user can elect to use for their convenience, or not.
[1] https://youtu.be/IzH54FpWAP0&t=530