Compatibility for BVH motion file in Unity is not a simple yes-or-no result. For import loss, list which features survive unchanged, which are translated, and which need a fallback.
For BVH motion file in Unity, reproduce the import once with logging enabled, then isolate the first feature that changes or disappears. Compare dropped properties before and after import instead of changing several exporter settings at once.
Compare source and destination properties directly, with special attention to silent omissions that do not trigger errors. Apply this import loss guidance to the actual BVH motion file in Unity delivery path.