问为什么不从窗体持有人触发WinForm Form.FormClosed事件？

EN

internal class FormA : Form
{
    public FormA()
    {
        this.Text = @"Form A";
    }
}

internal class FormAHolder
{
    internal FormA FormA { get; private set; }

    internal FormAHolder()
    {
        this.FormA = new FormA();
        this.FormA.FormClosed += this.OnFormAFormClosed;
    }

    private void OnFormAFormClosed(object sender, FormClosingEventArgs e)
    {
        Console.WriteLine("Hallo, please call me!!!");
        //// Clean up code should be here....
    }
}

internal class FormB : Form
{
    public FormB()
    {
        this.Text = @"Form B";
        var button = new Button { Text = @"Open Form A" };
        button.Click += this.OnButtonClick;
        this.Controls.Add(button);
    }

    private void OnButtonClick(object sender, EventArgs e)
    {
        var formAHolder = new FormAHolder();
        formAHolder.FormA.Show();
    }
}

[Test]
public void FormTest()
{
    var formB = new FormB();
    formB.ShowDialog();
}