Just adding more context about these limitations.
The implementation of server_groups and scheduler_hints in Watcher's cluster data model[1] was deferred to future releases, until we have it integrated with openstacksdk, as a replacement of python-novaclient library.
Even if we add information about server_groups and policies, strategies would also need to be updated to properly deal with these new constraints (which was not covered in this spec)
If you want to avoid failures due to affinity policy, you can try to exclude instances using audit scope[2].