MUC - Anonymous user presence changes

Okay, I’'m confused.

I have a registered user creating a MUC, and then have a client program which creates anonymous logins and joins the MUC.

I see the presence (available) messages when the anonymous users join. But when the anonymous user leaves, I don’'t get a presence message saying the user is now unavailable. The user still shows in the roster, etc etc…

I get expected results if I don’'t use anonymous logins, and see appropriate presence changes upon room exit…

Is this a bug, or design?