That doesn't seem to be correct. The manual states
"Allow user data modifications without identification : When your users are not identified by the system, do you allow them to modify their subscription?
If you select "No", then an identification message will be sent to the user with a link to enable him to modify his subscription.
If you select "Only his subscription" then his subscription will be updated but not his personal data.
If you select "Yes", the subscription and the data will be updated without extra identification."
All I want is to create a AcyMailing subscriber. There should be now Jommla membership required.