During the development of version 5.0, two cluster level privileges were added for the management of pipelines manage_pipeline and manage_ingest_pipelines. manage_ingest_pipelines was added as part of monitoring during an attempt to future proof monitoring documents with the use of an ingest pipeline that was empty. manage_pipeline was added as part of a role for the add data feature in Kibana. The manage_pipeline name was the name chosen by the security team at that time and the manage_ingest_pipelines name was not reviewed by the security team.

My opinion is that the manage_ingest_pipelines name should be deprecated and removed in favor of the manage_pipeline name based on the history.