Update SystemBackdropHost Spec for clarity

Clarified limitations of SystemBackdrop in WinUI3 compared to WinUI2 and improved wording for better understanding.

Author: godlytalias

specs/SystemBackdropHost Spec.md

@@ -4,11 +4,10 @@ SystemBackdropHost
 # Background
 
 There are some System backdrop materials such as Mica, Acrylic etc that are available in
-`Microsoft.UI.Xaml.Media.SystemBackdrop`. Today, its possible to host a system backdrop only at the window level and only for flyouts which makes
-it awkward to layer the effect behind individual containers / controls. This have been a major limitation on WinUI3 compared to WinUI2 in achieving the acrylic / mica effects.
+`Microsoft.UI.Xaml.Media.SystemBackdrop`. Today, its possible to host a system backdrop only at the window level and only for flyouts, not in a specific container / control level. This have been a major limitation on WinUI3 compared to WinUI2 in achieving the acrylic / mica effects.
 
 `SystemBackdropHost` is a lightweight `FrameworkElement` that bridges between the XAML tree and the composition
-infrastructure required by `SystemBackdrop`. It creates the composition link a backdrop needs, keeps the placement
+infrastructure required by `SystemBackdrop`. It creates the required composition components to host the systembackdrop on a specific container, keeps the placement
 visual sized to the arranged bounds, and applies the element's `CornerRadius` to the backdrop clip so rounded corners
 appear as expected. This control abstracts lot of details for the composition layer and hence make it easy
 for WinUI3 developers to implement the acrylic effect in the applications.