Yes, that is correct. Our Aweber integration only has us submit the buyer's name/email to Aweber, which then sends the buyer an opt-in confirmation email with a link they must click to confirm their subscription.
Also, while we can do this for every PayPal Standard/Express checkout because PayPal's checkout site does not provide a newsletter opt-in/-out preference, other checkout methods that provide a newsletter opt-in checkbox would require the buyer to tick that box to have us submit their info to Aweber.
If you require having all buyers subscribed to your mailing list, we'd recommend using MailChimp's E-junkie integration method instead:
http://kb.mailchimp.com/article/how-does-mailchimp-integrate-with-e-junkie/