But that's the same thing that would happen with any Harmony remote if your equipment has discrete on/off and input selection. What's happening is when you select an activity or OFF on the second remote, it's attempting to start or end the activity but because it's using discrete commands it appears as if nothing is happening.

If the second remote actually KNEW that you had started an activity on the first remote then it would change to the activity screen.

Your scenario would not work if your equipment did not use discretes. The remotes do not communicate with each other.