PR info added

Author: Anton Gubarenko

swiftui-expert-skill/references/view-structure.md

@@ -202,10 +202,16 @@ MyContainer {
 
 ## ZStack vs overlay/background
 
-Use `ZStack` to **compose multiple peer views** that should be layered together.
+Use `ZStack` to **compose multiple peer views** that should be layered together and jointly define layout.
 
-Prefer `overlay` / `background` when you’re **decorating a primary view without changing its measured size**.
-Use `ZStack` (or another container) when the “decoration” **must participate in layout sizing** (reserve space, extend visible/tappable bounds, avoid overlap with neighbors).
+Prefer `overlay` / `background` when you’re **decorating a primary view**.  
+Not primarily because they don’t affect layout size, but because they **express intent and improve readability**: the view being modified remains the clear layout anchor.
+
+A key difference is **size proposal behavior**:
+- In `overlay` / `background`, the child view implicitly adopts the size proposed to the parent when it doesn’t define its own size, making decorative attachments feel natural and predictable.
+- In `ZStack`, each child participates independently in layout, and no implicit size inheritance exists. This makes it better suited for peer composition, but less intuitive for simple decoration.
+
+Use `ZStack` (or another container) when the “decoration” **must explicitly participate in layout sizing**—for example, when reserving space, extending tappable/visible bounds, or preventing overlap with neighboring views.
 
 ### Examples: Choosing Between overlay/background and ZStack