SPFx Form Customizers - onSave method functionality

[Anthony Poulin (ynot3363)]

When you scaffold up an SPFx Form Customizer extension it comes with a the following private methods:

private _onSave = (): void => {
    // You MUST call this.formSaved() after you save the form.
    this.formSaved();
  };

  private _onClose = (): void => {
    // You MUST call this.formClosed() after you close the form.
    this.formClosed();
  };

The comments indicate that we MUST call these functions when the form is save or closed. I was wondering if anyone knew or Microsoft could provide clarity on what these functions actually and why we must call. From what I can gather from their minified code is that it logs engagement and then navigates the user back to the sourceUrl which is pulled from the Source query parameter and stored in context upon form load and if no param is found it is the webs relative site url.

The business reason behind the initial question is we have a need to route users to another page upon a successful entry that isn't the page they came from. To be able to do that we will need to for go calling these method.