Nintendo switch users can bypass realms security

Person A (in my household) owns a bedrock Realm and plays via XBox.  They have invited Person B into that Realm.  Person B, in a different household, is playing on Nintendo Switch.  Person C lives in the same household as Person B and is not invited into the Realm but they are actually able to enter the Realm.  As far as I can tell, this happens when Person B and C are playing locally on their Switch and when Person B joins the Realm then Person C can sneak in to the Realm too irrespective of the fact that they are not on the invite list.  Person A has no way of preventing Person C from accessing the Realm.