V23 included a new Metrics gRPC message in the GenerateBenchmarksMetricsResponse message: https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v23/services/benchmarks_service.proto#L351
This can potentially cause a naming clash with the Metrics message that contains generic reporting metrics.
In some client libraries this wasn't an issue because the messages live in different namespaces, but I wanted to give you a heads up about this potential issue.