The agent and the client are two separate components. You can only install the AutoSys client utilities using the AutoSys installation iso. There isn't an AutoSys iso that will install the 11.5 agent so you must use the agent-only iso for that agent version. That iso does not have an option for installing AutoSys client utilities.
If you want AutoSys client utilities installed on machines where you have installed an 11.5 agent, you will need to run a separate install for those using the AutoSys iso.