Planar Reflection Actor Unable To Add Actors On A Different Sublevel To Hidden Actors Array

Planar Reflection Actor can't add any actors that are on a different sublevel to the hidden actors/show only actors array.

1. Open attached project
2. In the scene select the planar reflection actor
3. Attemp to add the cube hovering above the floor to the hide actors list

RESULT
The field remains empty

EXPECTED
The Cube Mesh gets added to the hidden a

Planar reflections / "Hidden Actors" and "Show Only Actors" not working