The AUP is supposed to prevent the agent accumulating power. The AI initially has huge potential power (because its potential power is all the power it could ever accumulate, given its best strategy to accumulate power) and the penalty is supposed to prevent it turning that potential into actual power—as measured by AUP.
So the AI always has the power to build a subagent; that post just shows that it can do this without triggering the AUP-power penalty.
The AUP is supposed to prevent the agent accumulating power. The AI initially has huge potential power (because its potential power is all the power it could ever accumulate, given its best strategy to accumulate power) and the penalty is supposed to prevent it turning that potential into actual power—as measured by AUP.
So the AI always has the power to build a subagent; that post just shows that it can do this without triggering the AUP-power penalty.