Explanations in Episode 2 make it doubtful that the people of pso2 sales the Oracle Fleet may be descendents of both Pioneer II or its parent's civilization. Pioneer II had fundamental techniques and photon weapons, but photon technology was not known to the Oracle Fleet until a research boat found Xion, who taught it to them, and with her guidance the original Photoners became incredibly powerful. Pioneer II lost a few like photon arts, and would have to have broken following the discovery of Xion.

I believe that the background of Pioneer 1 and 2 separate themselves sufficient to describe that. Pioneer 2 and 1 were shipped out as ancient scouts for worlds. Ragol itself was among the worlds scouted for habitation and Pioneer 1 was shipped out as first tide, with the wave behind with Pioneer two. I believe that the photoners, those who seen Xion, were a part of another Pioneer ship (we will say 3 to the sake of clarification) which contribute to the growth of this Oracle Fleet.

Pioneer 3 is likely what was updated into the Oracle Mothership and let it salvage the rest of the culture that the Pioneer ships were intended to save. Given Luther's status, it indicates that the photoners may be equivalent to those who had been part of the Pioneer ships. It'd fall in line with the technology on Pioneer 1 and 2 and Xion being the advancement catalyst for what we use now. Spoilers Dark Falz out of PSO2 derive their power. The Profound Darkness is a corrupt clone of Xion.

Just one small hitch with this particular theory. We know what happened in PSO to the first civilization. Wherein we learn that at some stage they made an AI to renew Coral's environment. This AI was finally infected by D-Cells and went rogue and killed off 90 percent of civilization. Those paying attention will remember that D-Cells, were the actual reason behind the Pioneer project in the first place. D-Cells had forced it to Coral, through an asteroid or any such macguffin, along with the authorities wanted to weaponize it.

They put together the Pioneer job to track down the original source of the D-Cells, and discovered Ragol. Moving back to the point, PS0 occurs 100 years after culture gets nuked. Mother Trinity, the rogue AI, was created around the time of the events of cheap PSO2 Meseta or shortly after Episode III. Which is just another story thing that runs contrary to PSO2.