By definition, a chatroom has presence information about the occupants, because they use directed presence to join the room.
-Note: It is strongly NOT RECOMMENDED to use directed presence with Entity Capabilities data that differs from the data included in broadcast presence for the purpose of establishing implicit PEP subscriptions to another entity, because the directed presence information will be overwritten by any subsequent presence broadcast.
By default, the use of directed presence is used to establish a MEP subscription to the chatroom's eventing data. In order to filter which notifications are sent by the MEP service, the contact's client includes extended &xep0115; information in the directed presence notifications it sends to the chatroom. Because the MEP-enabled room supports the "filtered-notifications" feature, it sends only those notifications that match the occupant's expressed notification preferences.