If the CopyRefAssembly task finds that the destination .dll has the same MVID as the source, it will helpfully log a message that the copy is skipped:

However if it proceeds to copy the file over, it doesn't seem to log the message.

It would help for various analysis tools if it logged the same message as the MSBuild Copy task in case the file is copied:
"Copying ... to ..."
https://github.com/dotnet/msbuild/blob/e049bfe3dddb84270dec5fc1aaedc9664f77eb98/src/Tasks/Copy.cs#L303