Cannot override materials on instanced reference

**Describe the bug**
Cannot override materials on instanced reference using Stronger than Descendants.

**To Reproduce**
In the attached hip file, there are two references: one instanced, one not instanced.
The material override (green) applies to the non-instanced reference only.

[instance_material_overrides.v01.zip](https://github.com/user-attachments/files/19297706/instance_material_overrides.v01.zip)

Note: In Configure Primitives, if you change /world/instanced to /world/instanced/geom, then it works.

**Used Software Versions**
- Latest HtoA and Arnold as of 20250317

Start by opening instance_material_overrides.v01.zip in the reported HtoA and Arnold setup and reproduce the two-reference comparison. Inspect Configure Primitives for /world/instanced and /world/instanced/geom; done means the green material override behaves consistently for both instanced and non-instanced references when targeting /world/instanced.

Written by the indexing model from the issue text.