The BorderWidths other than top areignored even when the Region has no shape.
Here is a simple test app.

public class JavaFXTest extends Application {
  
  @Override
  public void start(Stage primaryStage) {
    Button btn = new Button();
    btn.setShape(null);
    btn.setBorder(new Border(new BorderStroke(Color.RED, BorderStrokeStyle.SOLID, CornerRadii.EMPTY, new BorderWidths(10,1,1,1))));

    btn.setText("Say 'Hello World'");
    btn.setOnAction(new EventHandler<ActionEvent>() {
      
      @Override
      public void handle(ActionEvent event) {
        System.out.println("Hello World!");
      }
    });
    
    StackPane root = new StackPane();
    root.getChildren().add(btn);
    
    Scene scene = new Scene(root, 300, 250);
    
    primaryStage.setTitle("Hello World!");
    primaryStage.setScene(scene);
    primaryStage.show();
  }

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