The docs only covers the case where the payment method is created by the frontend (JS). But there is a risk that the user leaves the website before the frontend sends the information to the backend that the card has been added (and its ID).
In order to make a payment, I need ID of the payment method. I don't want to query Stripe's API for user cards IDs every time before making a payment, so I want to save the payment method ID in my local database. I also want to allow the user to define more payment methods and choose the default one.