Retainer Box does not propagate Visibility settings to children

This is not a regression. Tested in //UE4/Release-4.27 CL18319896

Retainer Box does not propagate Visibility settings to children. Setting Canvas visibility to 'Not Hit-Testable (Self & All Children)' also does not change children of a Retainer Box.

1. Create or open any project
2. Create a new Widget Blueprint derived from the User Widget
   1. Add a Canvas Panel to the Widget
   2. Add a Retainer Box as a child of the Canvas Panel
   3. In the Retainer Box Details panel set Visibility to 'Not Hit-Testable (Self & All Children)'
   4. Add a Button as a child of the Retainer Box
   5. Compile, save, and close the Widget Blueprint
3. Open the level blueprint to add the Widget to screen
   1. Off of Event BeginPlay create a 'Create Widget' node
   2. Set the Class to the Widget we just made
   3. Get a reference to the Player controller and set it as the Owning Player
   4. Create an 'Add to Viewport' node set the Target as the Return value from the 'Create Widget' node
   5. From the Player Controller reference drag off and create a 'Set Show Mouse Cursor' node then set it to true
   6. Connect up execution pins
   7. Compile, save, and close the Level Blueprint
4. Play in Editor
5. Hover over the button

Expected Results:
The Button doesn't change to the hovered state, and isn't clickable.

Actual Results:
The Button changes to the hovered state, and is clickable. Any logic fired from an On Click event will be executed.