Update after review

src/Avalonia.Controls/Shapes/Rectangle.cs

@@ -21,7 +21,11 @@ namespace Avalonia.Controls.Shapes
 
         static Rectangle()
         {
-            AffectsGeometry<Rectangle>(BoundsProperty, StrokeThicknessProperty);
+            AffectsGeometry<Rectangle>(
+                BoundsProperty,
+                RadiusXProperty,
+                RadiusYProperty,
+                StrokeThicknessProperty);
         }
 
         /// <summary>

src/Avalonia.Visuals/Platform/IPlatformRenderInterface.cs

@@ -169,8 +169,12 @@ namespace Avalonia.Platform
         IGlyphRunImpl CreateGlyphRun(GlyphRun glyphRun);
 
         /// <summary>
-        /// Gets a value indicating whether the platform supports rectangles with rounded corners.
+        /// Gets a value indicating whether the platform directly supports rectangles with rounded corners.
         /// </summary>
+        /// <remarks>
+        /// Some platform renderers can't directly handle rounded corners on rectangles.
+        /// In this case, code that requires rounded corners must generate and retain a geometry instead.
+        /// </remarks>
         bool SupportsIndividualRoundRects { get; }
 
         /// <summary>