Confirmation email on WordPress registration

Why is it, when I enable the feature to sign on for the newsletter on WordPress account creation, that user receive an email confirmation even when they have not ticked the checkbox. If a new user don’t tick the newsletter checkbox (for newsletter X) they ar not added to the newsletter I configured (X, which is correct) but still get a confirmation e-mail (which is not correct).

I think it is because they automatically are added to the WordPress Users list too. And for that reason an confirmation email is sent? But I don’t use this list for my newsletter, I use only newsletter X for it instead.

How it should work (IMHO): if a new user on WP registration ticks the checkbox, they will be added to newsletter X and the WordPress Users group and receive a confirmation email. If a new user on WP registration DON’T ticks the checkbox, the y will be added to the WordPress Users group only and DON’T receive a confirmation e-mail