Every time someone signs up or logs in, our app does a check to see whether this email is for an existing customer or is someone completely new.
If this is an existing customer (matched by email), our app will simply bind the social login to their existing account. Please note that if an existing customer with email A logs in using Google but with email B, then we cannot know that they are the same customer. Binding to an existing customer account assumes they will use the same email. This is most often the case.
If this is a new customer, i.e. the email does not match anyone in your current database, we will create the new customer account with their name and email address + opt them into your subscriber list by default.