Walkable Slope Override not observed by ISMCs

A static mesh assets's Walkable Slope Override is observed by placed static meshes, but not by ISMC instances.

• Open the ThirdPerson template.
• Place an ISMC with one instance of the stairs mesh into the level.
• Notice how the character can walk over both the static mesh and ISMC stairs.
• Open the stairs mesh (the static mesh asset) and set Walkable Slope Behavior to 'Unwalkable'.
• Notice how the character can still walk over the ISMC, but not the static mesh.

Expected: The character shouldn't be able to walk over the ISMC.