mbf_costmap_nav publisher and subscriber of footprint topic at the same time

edit

by having a look on topics i found out that mbf_costmap_nav is publisher and subscriber at the same time of the local and global costmap/footprint topic:

rostopic info /mbf_costmap_nav/global_costmap/footprint
Type: geometry_msgs/PolygonStamped

Publishers: 
 * /mbf_costmap_nav (http://127.0.0.1:35613/)

Subscribers: 
 * /mbf_costmap_nav (http://127.0.0.1:35613/)

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rostopic info /mbf_costmap_nav/local_costmap/footprint
Type: geometry_msgs/PolygonStamped

Publishers: 
 * /mbf_costmap_nav (http://127.0.0.1:35613/)

Subscribers: 
 * /rviz (http://127.0.0.1:42127/)
 * /mbf_costmap_nav (http://127.0.0.1:35613/)

Is it intended to be so or how can i avoid this?