Merge Actors (Simplify) is broken with Substrate Shader Models Node

Substrate Materials cannot be baked when Meshes are merged using the "Simplify" method. All textures except for the normal are reduced to a single black parameter. The normal texture produced does not contain details from the normal of the baked Materials.

Also reproduced in UE 5.6.1, CL: 45232827

1. Download the attached test project and open (5.6 or 5.7)
2. Observe the Material "M_SubstrateMat" uses three textures: Diffuse, Masks, and Normal (textures from Starter Content)
3. Select the two actors "Cube" and "Sphere".
4. In the Actor menu, Select "Merge (2)" -> "Simplify"
5. Select a folder for the simplified assets (such as /Game/Merge/)
6. Observe the merged Material only uses the Normal texture channel, and only a Normal texture was baked.
7. Observe that the produced normal texture does not have the detail of the brick normal texture used by the original Material.