The source is Nolatrav saying they factored TL into their prototype economic rating a few posts up.
"The real reason I mentioned it however is because I've been developing a simple economic rating for worlds, based on Pop, TL, Gov, Law, Trade Codes and surrounding starports."
Or are you asking me to cite my sources about the difference between actual sentients' economic activity and that of non sentient robots? Because that's just RL. Robots are good for productivity even at our TL. But they don't produce the wide ranging creative impact on the economy that actual humans do. And, until they are sentient, they won't do so. A droid is no more population than a self driving car, which is also a robot.
The exception would be, as I mentioned, when you don't have a tech level to support robotic industry and are using droids as if they were human manual laborers. Though they still wouldn't be as economically valuable as sentients overall because of how narrow their output is.