Comment 2 for bug 1708458

If we wanted to expose something specific out of the REST API, then we'd likely need to move that data to a different field out of the instance_system_metadata table and then make it part of the API contract, more like a field on the instance itself, or something related, but the point being you'd only expose specific things you care about, not all of system_metadata which is meant to be internal to Nova and can change at any point, so it can't be part of an end user API contract. This would also require a microversion for the compute REST API. It's definitely not a bug and Nova doesn't do RFEs via launchpad bugs. For information on the Nova blueprint process, see:

https://docs.openstack.org/nova/latest/contributor/blueprints.html