Glad this is working for you. I noticed the error in the doc as well, working on getting that fixed .
In regards to your most recent update- It looks like the users are getting a verification email with this rule regardless of whether or not there are verified. Typically you would want to add a conditional that performs the callback if the user is already verified.
if (user.email_verified) {
return callback(null, user, context);
} else {
//Your email verification logic
}
Let me know if that fixes it.