Standardisation at the format level will help with portability across different platform implementations.

This "standardization" is pretty kludgey if you have to docker pull then docker export.

I think that's because OCI currently only has a specification for the runtime, not the distributable image. But it seems like as of a few weeks ago, work is underway to standardize the distributable image as well: https://github.com/opencontainers/image-spec