If you modify a Deployment group, it re-deploys the existing agents with the updated configuration. However, if you have not deployed an agent with the deployment group, then even if you are using the same host, the configurations are not applied to that agent.

Each Smart Agent can be assigned to a single Deployment Group, and assigning the Smart Agent to another deployment group will remove the Smart Agent from the previous deployment group. The configured agents from the new deployment group are installed over the agents from the previous deployment group.