Helm proxy - mirrored artifacts unable to be exposed after remote stops supplying version in index.yaml

For the helm proxy I expect the downloaded packages to always be available and exposed regardless if the third party decided to deprecate or stop supplying a specific version. Unfortunately, this is not the case for the helm proxy repository currently  even if the proxy has a previously  downloaded   version that remote is no longer supplying; this artifact is not  exposed since the index.yaml is coming directly from the remote.