Hi @DanGoyette, so about the first query, please note that these sub-folder names mostly correspond to the asset IDs used in Bridge for these assets. This naming convention is intended to help users easily reference the assets in Bridge. Please see the attachment below:
However, if you have any suggestions regarding this, please feel free to share.
Now about the folders that do not contain FBX files, these assets are designed as 2D textures. For instance, the asset ID highlighted in the screenshot above is from African Slate Quarry | Fab and is a surface asset. Such assets will only include texture files, without any .fbx files.