Run the code:


import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class JavaApplication2 extends Application {

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

    @Override
    public void start(Stage stage) throws Exception {
        final TextField tf = new TextField("Text text");

        Button b = new Button("Select next word");
        b.setOnAction(new EventHandler<ActionEvent>() {

            @Override
            public void handle(ActionEvent t) {
                new Thread(new Runnable() {

                    @Override
                    public void run() {
                        try {
                            Thread.sleep(3000);
                        } catch (InterruptedException ex) {
                            Logger.getLogger(JavaApplication2.class.getName()).log(Level.SEVERE, null, ex);
                        }
                        Platform.runLater(new Runnable() {

                            @Override
                            public void run() {
                                tf.selectNextWord();// can replace with tf.nextWord();
                            }
                        });
                    }
                }).start();
            }
        });

        VBox vb = new VBox();
        vb.getChildren().addAll(tf, b);
        Scene scene = new Scene(vb, 300, 300);
        stage.setScene(scene);
        stage.show();
    }
}

Put caret in the first word, and press ctrl+shift+right. See the selection (till the end of the word).
Click button, and see the selection, putting caret into the first word, and waiting 3 seconds. It is till the beginning of the next word.

That is difference.