ProjectGeneratorPeers: difference between createPanel and buildUI

I'm trying to better understand how the "New Project" dialogs work.

While looking at the sample plugin for AngularJS, I noticed that the constructor for `AngularCLIProjectGeneratorPeer` calls a function called `createPanel()` which looks like it initializes all of the different settings fields that will show up in the project wizard.

What I expected to happen was that when I select my new project type the panel created from `createPanel()` would be displayed. This is not the case though. In order to get the fields to show up I actually had to implement the `buildUI()` function and add the fields again to the setting step

So my question is what is the purpose of the `createPanel()` function and how is it different from `buildUI()`

Abridged code looks somethng like for AngularCLIProjectGeneratorPeer

private class AngularCLIProjectGeneratorPeer extends NpmPackageGeneratorPeer {

    private TextAccessor myContentRoot;

    private SchematicOptionsTextField myOptionsTextField;
    private JCheckBox myUseDefaults;

    @Override
    protected JPanel createPanel() { // result returned from this.getComponent()
      final JPanel panel = super.createPanel();

      myOptionsTextField = new SchematicOptionsTextField(ProjectManager.getInstance().getDefaultProject(),
                                                         Collections.emptyList());
      myOptionsTextField.setVariants(Collections.singletonList(new Option("test")));

      LabeledComponent component = LabeledComponent.create(
        myOptionsTextField, Angular2Bundle.message("angular.action.new-project.label-additional-parameters"));
      component.setAnchor((JComponent)panel.getComponent(0));
      component.setLabelLocation(BorderLayout.WEST);
      panel.add(component);

      myUseDefaults = new JCheckBox(Angular2Bundle.message("angular.action.new-project.label-defaults"), true);
      panel.add(myUseDefaults);

      return panel;
    }

    @Override
    public void buildUI(@NotNull SettingsStep settingsStep) {
      super.buildUI(settingsStep);
      final ModuleNameLocationSettings field = settingsStep.getModuleNameLocationSettings();
      if (field != null) {
        myContentRoot = new TextAccessor() {
          @Override
          public void setText(@NotNull String text) {
            field.setModuleContentRoot(text);
          }

          @Override
          @NotNull
          public String getText() {
            return field.getModuleContentRoot();
          }
        };
      }
      settingsStep.addSettingsField(UIUtil.replaceMnemonicAmpersand(
        Angular2Bundle.message("angular.action.new-project.label-additional-parameters")), myOptionsTextField);
      settingsStep.addSettingsComponent(myUseDefaults);
      getPackageField().addSelectionListener(this::nodePackageChanged);
      nodePackageChanged(getPackageField().getSelected());
    }
  }