Hi @yaakov-smith_7984 ,
This behavior is expected and by design. "Deprecation" and "Unlisted" are server-side metadata (i.e. stored in the remote repository, not the package itself), and once a package is brought into to a different server (i.e. ProGet), it's "disconnected" from the other server.
That being said, there is a feature in ProGet that can routinely "sync" this server-side metadata:
https://docs.inedo.com/docs/proget/sca/howto-deprecated-package-alerts
https://docs.inedo.com/docs/proget/sca/policies#oss-metadata-updating-caching
This feature obviously comes with some performance costs, though you'd really have to enable it to see if that has any impact on operation.
Another approach is to use a retention policy that deletes cached packages older than 90 days.
Thanks,
Steve