Anonymous users and subscribtions

Hi all,

I'm trying to set-up a server accepting anonymous accounts (for demo purposes). And get those users to subscribe to each other presence.
I have some difficulties testing with just two clients, but I'm unsure if I understand the expected behavior correctly. Here are some setup I tried .

Server set with auth_method=internal only, two users are registered with a pw:
- users can login using their pw and subscribe to each other no problem. Works as I though it would
- at last I know the client part if working as expected.

Server set with auth_method=anonymous only, two users cannot be registered (normal)
- users can login anonymously (empty pw), but they don't receive the presence subscription from the other client. I was expecting them to receive the subscription.

Server set with auth_method=internal and anonymous, two users are not registered
- users can login anonymously (empty pw), but they don't receive the presence subscription from the other client. (same a before)

Server set with auth_method=internal and anonymous, two users are registered with a pw
- users cannot login with their password. (I was expecting this to work)
- users can login anonymously (empty pw), and they can subscribe to each other.

Is that normal that the users have to be registered to make the the subscription work in anonymous?
Is that normal that registered users cannot log in with the registered password on anonymous/internal auth?

Seems there was a similar issue on an older version: https://www.ejabberd.im/node/24927
But not sure if it's really related.

I'm using ejabberd 15.11 (more precisely I'm using a docker: https://hub.docker.com/r/rroemhild/ejabberd/)

Thanks for the help