Collection Instances should NOT flatten on FBX export.

Collection Instances are among the most powerful features in Blender, yet they have a significant limitation. When exporting to FBX, Blender currently flattens the hierarchy of the respective Collection Instances.

For instance, consider a scenario where I create a Mechanical Spider in Blender, intending to import it into Unity. The spider has 8 identical legs. To animate the hierarchy without using bones, I arrange the LowerLeg under the UpperLeg, creating a chain similar to an FK joint. This mechanical leg also includes several other moving parts, which need to be strategically organized within the leg's hierarchy.

I construct one leg within a Collection and then replicate it across the spider using Collection Instances. This approach allows me to modify one leg in the Collection, and the changes automatically apply to all legs.

However, a major issue arises when exporting the spider as an FBX file into Unity: the hierarchy of each leg is flattened. This flattening prevents me from moving the legs as originally intended, as the LowerLeg is no longer nested under the UpperLeg.

While Collection Instances are incredibly powerful in Blender, their full potential in production is hindered without the ability to export with the original hierarchy of the referenced Collection.