Users being added to Newsletter

In the settings I have "Wordpress user registration" set to "Disable". Users cannot register themselves on this blog, however it is a multi-author blog, an every time I add or edit a contributor they are added to the Newsletter Members. Should it not be checking that the user registration is set to Disable to not do this? Also, I have "Double opt-in" set to "Enable" - so even when they are added to the Newsletter Members I don't see any way to confirm them even if I did want them to be added to the list.