There were survivors on this planet.
The existence of survivors had inspired Hao Ren and aroused his curiosity. He was so excited that he had temporarily forgotten the shit he was now in after his spacecraft crashed on this planet. In the doomsday world of the Plane of Dreams, the number of First Borns and the planets that they destroyed was by no means few. The many images of ruins that the drones sent back had proven this. But there were few survivors. And survivors who still stubbornly resisted the purge were unheard of so far. But the appearance of the aircraft earlier meant that the survivors were not only resisting but they seemed to be in control.
Hao Ren did not want to make contact with those aircraft. Instead, he had the MDT keeping an eye on them and intercepting their radio communication. He was just waiting for the right time to make contact with the survivors.