rosapi: how to filter topics

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I am trying to understand rosapi.

Here is my test:

1. Launching some of my own ros nodes
2. Doing rostopic list reveals a long list of topics
3. Launching rosapi with a launch file that sets the topics_glob param. The console output confirms that the topics_glob is set as expected:

SUMMARY
========

PARAMETERS
 * /rosapi/params_glob: [*]
 * /rosapi/services_glob: [*]
 * /rosapi/topics_glob: [/rosout]
 * /rosdistro: kinetic
 * /rosversion: 1.12.13

But when I then do rosservice call /rosapi/topics, all existing topics are listed, incl /rosout. I expected to see only the /rosout listed due to the topics_glob.

Are my expectations wrong? What is the right use of the *_glob parameters?