libgazebo_ros_api_plugin.so question

edit

The gazebo_ros_api_plugin is a SystemPlugin. The gazebo plugin tutorial says the following about SystemPlugin's:

The System plugin is specified on the command line, and loads first during a Gazebo startup.
This plugin gives the user control over the startup process.

I'm not completely familiar with the architecture, but I believe it needs to be a SystemPlugin in order to connect with ROS during startup. Thus it needs to be specified on the command-line. I believe the scripts called by launch files take care of this.

Does this answer your question?