Production entails manufacturing, requiring funds and raw materials. The manas lacks these elements; it has no repository and cannot store anything. Only the Tathāgatagarbha possesses all such dharmas, containing the seeds of all phenomena, enabling it to create all dharmas. This is analogous to the role of film production. The Tathāgatagarbha produces based on karmic seeds; karmic seeds represent the choices made by the Tathāgatagarbha, and this constitutes conditioned dharmas.
The Tathāgatagarbha also possesses conditioned nature; all dharmas are produced through its conditioned activity. If the Tathāgatagarbha were entirely unconditioned and completely uninvolved, the world would neither arise nor exist, the five aggregates would not manifest, and even the manas itself would not exist. The nature of what is produced is indeed determined by the Tathāgatagarbha, not by the manas, which lacks autonomy. Once the "production" is determined, the corresponding karmic retribution is set, and cause and effect are thereby recompensed.
1
+1