The documentation for aws2-s3 says that the component supports S3 custom metadata headers. After looking at the code it isn't implemented there.
The integration I'm implementing hinges on using the custom-metadata in aws s3. I think this is something others could benefit from as well.
We are currently on 3.11.3 so I used that for the ticket but this does affect all 3.11.X versions.
I know this is a feature that was available with the SDK v1 version.