the skin doesn't keep the initial setting of area's scrollTop, but resets it to 0.

To reproduce, run the example below which sets the scrollTop to > 0: on showing the top is 0. Programmatically setting it while showing, behaves as expected.

public class TextAreaScrollTop extends Application {

    private Parent createContent() {
        TextArea area = new TextArea(LOREM_IPSUM + LOREM_IPSUM);
        area.setWrapText(true);
        // inital value
        area.setScrollTop(100);
       
        Button setScrollTop = new Button("set scrollTop");
        setScrollTop.setOnAction(e -> {
            area.setScrollTop(100);
        });
        
        // visualize scrollTop
        Label scrollTop = new Label("scrollTop: ");
        Label scrollTopValue = new Label();
        scrollTopValue.textProperty().bind(area.scrollTopProperty().asString());
        VBox content = new VBox(10,
                new HBox(10, scrollTop, scrollTopValue),
                area,
                new HBox(10, setScrollTop));
        return content;
    }

    @Override
    public void start(Stage stage) throws Exception {
        stage.setScene(new Scene(createContent()));
        stage.show();
    }

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

    public final static String LOREM_IPSUM = "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, "
            + "sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, "
            + "sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. "
            + "Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. "
            + "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor "
            + "invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et "
            + "accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata "
            + "sanctus est Lorem ipsum dolor sit amet.";

}