ScrollBars in MDIForm are shown in run-time, when the MDIForm is unable to show the child Window completely. This can be because of the position of the child form.
Try this:
When ScrollBars property of MDIForm is True, drag the child so that is goes out of scope of the MDIForm. You will see the scrollbars then on the MDI Form. Also you will see them when you enlarge the child form in code. For example set the width of the child form in MDIForm_Load event handler this way:
Form1.Width = 20000
Since the MDIForm is smaller than this, you will see the horizontal scrollbars.
I hope this helps.