dynamic reconfigure callback happens automatically when a node is launched without rqt client

I am using dynamic_reconfigure in my node to adjust some params dynamically. I found that the first callback for dynamic reconfigure happens when the node is launched, specifically when I define the callback for dynamic reconfigure in my constructor. This causes my node to reject param values defined in my launch file and take in default values defined in cfg file for dynamic reconfigure. I would expect the callback to happen only when I launch rqt_dynamic_reconfigure which sets up a client, not when I set up the server in my node. At least a regular ROS server and client works this way, not callback on server side until a client makes calls to that server. In the implementation of dynamic reconfigure, is there a way to not have the callback happen when server is set up and only change param values when I launch rqt_dynamic_reconfigure?