but was actually overwritten.
not overwritten.... Imagine a you add a panel to your Main.root (which in it self is a panel), lets call it Panel1. Then you add a second panel to Panel1, let's call it panel2. If both panels have the anchor points set to be 0 Top, 0 FromRight, 0 Left, 0 FromBottom, then they occupy entirely their parent, but they do NOT overwrite them....
Panel2 parent is STILL panel1, and panel1 parent is STILL root.
If however, you set, lets say Panel2 to be 50% from Left, 0 from right, 50% from top, 0 from bottom, thus occupying 25% of panel 1, any control/view placed in Panel1 within those un-occupied 75% are still visible!