Websites using Facebook login usually don't ask for any of your Facebook information, just your email address. They also implicitly have the public information

Websites using Facebook login usually don't ask for any of your Facebook information, just your email address. They also implicitly have the public information on your profile since they have your Facebook ID, and I suppose it does reveal information to say that this user and email address is associated with this public Facebook profile. But they definitely don't get anything close to the read permissions you have on Facebook. Looking through some of my Facebook apps: Headspace, Stack Exchange, and Netflix only have my email address. Venmo is an example that asks for my friend list because they want to use it for social features.