If we’re worried about all possible paths from AI progress to human extinction, I think these conditions are too strong. The system doesn’t need to be an agent. As avturchin points out, even if it is an agent, it doesn’t need to be able to act in the real world. It doesn’t even need to be able to accept human extermination as a goal. All that is required is that a human user be able to use it to form a plan that will lead to human extinction. Also, I think this is something that many people working on AI safety have realized — though you are correct that most research attention has been devoted (rather inexplicably, in my opinion) to worries about superintelligent systems.
If we’re worried about all possible paths from AI progress to human extinction, I think these conditions are too strong. The system doesn’t need to be an agent. As avturchin points out, even if it is an agent, it doesn’t need to be able to act in the real world. It doesn’t even need to be able to accept human extermination as a goal. All that is required is that a human user be able to use it to form a plan that will lead to human extinction. Also, I think this is something that many people working on AI safety have realized — though you are correct that most research attention has been devoted (rather inexplicably, in my opinion) to worries about superintelligent systems.