That's because you're looking in the wrong place. Input selection is done at the device level - the activity only tells the device which input to use and the device figures it out from there. So go back and check the input setup for each device (Device->Options->Adjust Inputs). In your case you can setup the TV to just have one input (component 1) since that's all you'll be using. Sounds like your activity is choosing the Aux input on the receiver (re-run the activity setup) or you have the wrong command associated with the receiver input selection. Re-run the setup adjustment for the receiver.

You can go into Device mode and try the various input selection commands so that you know which ones to use. If your devices use a cycle input selection (cycles through the various options) your input list must match the device exactly. If you have discretes (one button always goes to a specific input) then the order doesn't matter.