Bumping to Houdini Version: 13.0.586
Houdini Engine Version: 1.8 (API: 19)
We no longer add a HoudiniAssetInput component onto the GameObject dragged in as a geo input for a Houdini asset. By default, we just take the Mesh from the MeshFilter of the dragged in GameObject and use that (in a read-only way) as the geo input.

If you still want to add attributes, paint, or modify mesh point data, on the input GameObject you now need to explicitly convert it into a Houdini Input asset by either adding the HoudiniAssetInput Component or using the Houdini Engine > Convert to Input Asset menu.