Currently node_view.inc does not execute the normal Drupal hooks, e.g. hook_node_view and hook_entity_view. In order for several other modules to work correctly, e.g. Metatag, these hooks must be executed.
Currently the node_content.inc plugin uses node_invoke($node, 'view') to trigger node_view(), which means that several key node-related and entity-related hooks do not get triggered unless that pane is added to the page. Several modules, include Metatag, depend on entity hooks triggering on entity view pages, which won't happen. I suggest moving the entity/node view logic to node_view.inc, and trim the node_content.inc logic to just building the final output.
PASSED: [[SimpleTest]]: [MySQL] 121 pass(es).