SplitPane, TableView, treeTableView behavior

public class test extends Application {

     private TableView<Person> table = new TableView<Person>();
        private final ObservableList<Person> data =
                FXCollections.observableArrayList(
                new Person("Jacob", "Smith", "jacob.smith@example.com"),
                new Person("Isabella", "Johnson", "isabella.johnson@example.com"),
                new Person("Ethan", "Williams", "ethan.williams@example.com"),
                new Person("Emma", "Jones", "emma.jones@example.com"),
                new Person("Michael", "Brown", "michael.brown@example.com"));
        final HBox hb = new HBox();

        public static void main(String[] args) {
            launch(args);
        }

        @Override
        public void start(Stage stage) {
            Scene scene = new Scene(new Group());
            stage.setTitle("Table View Sample");
            stage.setWidth(450);
            stage.setHeight(550);
            SplitPane splitPane = new SplitPane();
            splitPane.setOrientation(Orientation.VERTICAL);

            //TREETABLECOLUMN
            TreeTableView<Person> treeTableView = new TreeTableView<>();
            TreeTableColumn temp = new TreeTableColumn("First Name");
            temp.setMinWidth(100);
            temp.setCellValueFactory(
                    new PropertyValueFactory<Person, String>("firstName"));

            TreeTableColumn temp2 = new TreeTableColumn("Last Name");
            temp2.setMinWidth(100);
            temp2.setCellValueFactory(
                    new PropertyValueFactory<Person, String>("lastName"));

            TreeTableColumn temp3 = new TreeTableColumn("Email");
            temp3.setMinWidth(200);
            temp3.setCellValueFactory(
                    new PropertyValueFactory<Person, String>("email"));

            //treeTableView.setItems(data);
            treeTableView.getColumns().addAll(temp, temp2, temp3);

            //TABLE
            table.setEditable(true);
            //This is important to notice the left and right selection not working
            table.getSelectionModel().setCellSelectionEnabled(true);
            TableColumn firstNameCol = new TableColumn("First Name");
            firstNameCol.setMinWidth(100);
            firstNameCol.setCellValueFactory(
                    new PropertyValueFactory<Person, String>("firstName"));

            TableColumn lastNameCol = new TableColumn("Last Name");
            lastNameCol.setMinWidth(100);
            lastNameCol.setCellValueFactory(
                    new PropertyValueFactory<Person, String>("lastName"));

            TableColumn emailCol = new TableColumn("Email");
            emailCol.setMinWidth(200);
            emailCol.setCellValueFactory(
                    new PropertyValueFactory<Person, String>("email"));

            table.setItems(data);
            table.getColumns().addAll(firstNameCol, lastNameCol, emailCol);

            final TextField addFirstName = new TextField();
            addFirstName.setPromptText("First Name");
            addFirstName.setMaxWidth(firstNameCol.getPrefWidth());
            final TextField addLastName = new TextField();
            addLastName.setMaxWidth(lastNameCol.getPrefWidth());
            addLastName.setPromptText("Last Name");
            final TextField addEmail = new TextField();
            addEmail.setMaxWidth(emailCol.getPrefWidth());
            addEmail.setPromptText("Email");

            final Button addButton = new Button("Add");
            addButton.setOnAction(new EventHandler<ActionEvent>() {
                @Override
                public void handle(ActionEvent e) {
                    data.add(new Person(
                            addFirstName.getText(),
                            addLastName.getText(),
                            addEmail.getText()));
                    addFirstName.clear();
                    addLastName.clear();
                    addEmail.clear();
                }
            });

            /**
             * Try to add the TableView first and then the treeTableView,
             * you will see that selection left and right are working.
             *
             */
            //I add the TreeTableView FIRST
            splitPane.getItems().add(treeTableView);
            //Then I add the tableView
            splitPane.getItems().add(table);

            //Second case working
            //I add the tableView FIRST
            //splitPane.getItems().add(table);
            //Then I add the TreeTableView
            //splitPane.getItems().add(treeTableView);

            ((Group) scene.getRoot()).getChildren().addAll(splitPane);

            stage.setScene(scene);
            stage.show();
        }

        public static class Person {

            private final SimpleStringProperty firstName;
            private final SimpleStringProperty lastName;
            private final SimpleStringProperty email;

            private Person(String fName, String lName, String email) {
                this.firstName = new SimpleStringProperty(fName);
                this.lastName = new SimpleStringProperty(lName);
                this.email = new SimpleStringProperty(email);
            }

            public String getFirstName() {
                return firstName.get();
            }

            public void setFirstName(String fName) {
                firstName.set(fName);
            }

            public String getLastName() {
                return lastName.get();
            }

            public void setLastName(String fName) {
                lastName.set(fName);
            }

            public String getEmail() {
                return email.get();
            }

            public void setEmail(String fName) {
                email.set(fName);
            }
        }
    }