Hi,
this is exactly the case.
it seems that Apple Mail doesn't like "unsubscribe" link in the list header and really wants to send an email instead of directly unsubscribing users
Next version will add parameter in AcyMailing where you will be able to choose to show unsubscribe header link or not
That way, your users will be able (if disabled) to unsubscribe only from unsubscribe link from email