Animated Alembic vs Custom Depth Pass


I’m attempting an alembic workflow for animated characters. I’m also using a toon-style shader that utilises a Post Process material. It appears to work fine on a static Alembic object. I check ’ RenderCustom Depth on the outliner object Render Properties and it picks up the material.

The problem arises with animated alembic caches. The character appears animated as expected but setting the Render CustomDepth Pass doesn’t change render style. If I change the viewport view to visualise the depth buffer, the other objects appear but not the animated alembic object.

Is this a bug or is there something else I need to do to get the animated alembic file ‘seen’ in the depth buffer?