Red and green channels work as they should, but the blue channel is completely ignored, assumed 100%. Okay, it’s mostly never used, so rarely I’m absolutely not surprised nobody ever noticed this, but there is a use-case specific to Tower Unite (if it worked).
For context, a value of less than 100% in the blue channel reduces the strength of the reflection regardless of the normals - even on flat faces with flat 50%/50% Red/Green channels.
With limited material slots on workshop items and no functionality for using maps for specular/metallic/roughness maps, the blue channel could be used to affect the strength of the metallic/specular shading across the material, which even if there are no maps to utilise, would still be very useful for having multiple values across a texture atlas and help overcome that limitation.
It works in Unreal Engine’s normal maps and even displays the same way in Blender, but specifically not in Tower Unite’s workshop items, neither in the editor nor condos.