BUG: The “Unsubscribe” link above emails (for emails that support it) does not use the correct alias email to send the unsubscribe request. It uses the default email address, which is not necessarily the email address that the email was sent to and therefore not the correct from address to send to the unsubscribe link.
I also noticed that before when repeated unsubscribes had no effect. You would think that because Reply uses the correct alias address, unsubscribe would as well.
If you have a Pro License, you could open a support ticket so that the developers can correct it.