I've updated branch usd-importer-T81257-merge with the following changes to the UV import code:
Added code to handle UV primvars with Vertex interpolation, as these were being imported incorrectly. (See the attached images of a test case importing the NVIDIA Attic scene ball prop, which has Vertex UVs, before and after the change.)
Added logic to import indexed UVs.
Fixed UV winding order bug for left-handed orientation.
I've updated branch usd-importer-T81257-merge with the following changes to the UV import code:
Link to commit:
https://github.com/tangent-opensource/blender/commit/4c6839010b4ddfadc6bf0f3b32f492489abe4ccc