Scaling a path, were the x and y scale factors are slightly different leads to wrong result of getBoundsInParent.
If the scale factors are identical the result is correct.

See the following testcase:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.shape.ClosePath;
import javafx.scene.shape.LineTo;
import javafx.scene.shape.MoveTo;
import javafx.scene.shape.Path;
import javafx.scene.shape.StrokeType;
import javafx.scene.transform.Scale;
import javafx.stage.Stage;


public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception {
    
     Path path = new Path(new MoveTo(20, 0), new LineTo(20, 20), new LineTo(0, 20), new LineTo(0, 0), new ClosePath());
     path.setFill(javafx.scene.paint.Color.BLACK);
     path.setStrokeType(StrokeType.CENTERED);
     Pane pane = new Pane();
     pane.getChildren().add(path);
    
        primaryStage.setTitle("Path scaling");
        primaryStage.setScene(new Scene(pane, 242, 242));
        primaryStage.show();
        
        // correct
        // if x and y scale factors are identical
        Scale scale = new Scale(10.9793640000000, 10.9793640000000);
        path.getTransforms().setAll(scale);
        System.out.println(String.format("path width after: %f", path.getBoundsInParent().getWidth()));
        System.out.println("correct width: 241.546021");
        
        // not correct
        // if x and y scale factors slightly different
        System.out.println(String.format("path width before: %f", path.getBoundsInParent().getWidth()));
        scale = new Scale(10.9793640000000, 10.9793640000001);

        path.getTransforms().setAll(scale);
        System.out.println(String.format("path width after: %f", path.getBoundsInParent().getWidth()));
        System.out.println("not correct! expected width: 241.546021");
        
    }

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