What happens when we don't use AsyncOpen or AutoOpen?

MongoDB Atlas App Services & Realm
1

I am using either the default configuration or sync configuration depending on whether there is a logged in user.

struct ContentView: View {
    
    @ObservedObject var app = Realm.app
    
    var body: some View {
        if let config = app.createFlexibleConfiguration() {
            MainScreen()
                .environment(\.realmConfiguration, config)
                .environmentObject(app)
        } else {
            MainScreen()
                .environmentObject(app)
        }
    }
}

extension Realm {
    static let app = RealmSwift.App(id: Config.APP_ID)
}

extension App {
    func createFlexibleConfiguration() -> Realm.Configuration? {
        if let user = self.currentUser {
            let config = user.flexibleSyncConfiguration(initialSubscriptions: { subs in
                if subs.first(named: "user_items")  == nil {
                    subs.append(QuerySubscription<Item>(name: "user_items") {
                        $0.userId == user.id
                    })
                }
            })
            return config
        }
        return nil
    }
}

Full code

It seems to be working as expected already so I am wondering if I even need to use AutoOpen. (If I login anonymously, a new user is created and no items are displayed. If I log out, I see the items I created before logging in.) Is it “downloading synced changes before opening the realm”, but without listening to the progress (case .progress)?