event_pipeline allows non-unique source names

event_pipeline.yaml:
---
sources:
    - name: snapshot_source
      events:
          - "snapshot.create.start"
          - "snapshot.create.end"
          - "snapshot.update.start"
          - "snapshot.update.end"
      sinks:
          - snapshot_sink
    - name: snapshot_source
      events:
          - "volume.create.start"
          - "volume.create.end"
          - "volume.update.start"
          - "volume.update.end"
      sinks:
          - volume_sink
sinks:
    - name: snapshot_sink
      transformers:
      triggers:
      publishers:
          - notifier://
    - name: volume_sink
      transformers:
      triggers:
      publishers:
          - notifier://

excerpt from agent-notificaiton.log
...
2015-06-17 17:29:22.169 89692 DEBUG ceilometer.pipeline [-] Pipeline config file: /etc/ceilometer/event_pipeline.yaml _setup_pipeline_manager /usr/lib/python2.7/site-packages/ceilometer/pipeline.py:673
2015-06-17 17:29:22.178 89692 INFO ceilometer.pipeline [-] Pipeline config: {'sources': [{'events': ['snapshot.create.start', 'snapshot.create.end', 'snapshot.update.start', 'snapshot.update.end'], 'name': 'snap
shot_source', 'sinks': ['snapshot_sink']}, {'events': ['volume.create.start', 'volume.create.end', 'volume.update.start', 'volume.update.end'], 'name': 'snapshot_source', 'sinks': ['volume_sink']}], 'sinks': [{'
publishers': ['notifier://'], 'transformers': None, 'name': 'snapshot_sink', 'triggers': None}, {'publishers': ['notifier://'], 'transformers': None, 'name': 'volume_sink', 'triggers': None}]}
2015-06-17 17:29:22.178 89692 INFO ceilometer.pipeline [-] detected decoupled pipeline config format
...

Hence question - why "source" names from event_pipeline ain't checked in the same way as "sink" names do?

Thanks,
Yurii