Does NavArea on StaticMeshes only work with Convex Collision?

Hi everyone,

I can’t figure why NavArea seems to only work when using a Convex Collision with “Gather Convex Geometry” option turned On with Static Meshes?
In that screenshot, if I disable that option, the pink area totally disappears.
I tried to play with Simple and Complex collision and this new collision is a convex one each time.

Any idea on how generate a NavArea only for the Torus itself?