Historical explanations in Episode 2 make it doubtful that the Oracle Fleet's people may be descendents of Pioneer II or its parent civilization. Pioneer II had basic tactics and photon weapons, but photon technologies wasn't known to the Oracle Fleet before a study ship found Xion, who taught them, and with her advice the original Photoners became incredibly strong. Pioneer II would have to get split after the discovery of Xion from the fleet, and lost a few of its advanced photon technology like photon arts.
I believe the history of Pioneer 1 and two separate themselves enough to explain that. Pioneer 2 and 1 were sent out as early scouts for habitable worlds. Ragol itself was among the probable worlds scouted for Pioneer 1 and habitation was shipped out with Pioneer 2 closely behind with the wave. Pioneer 1 was deconstructed and used as building material for Pioneer 2 and the colony orbited Ragol throughout PSO's events. I feel that the photoners, those who visited Xion, were part of another Pioneer boat (we will say 3 for the sake of caution ) which contribute to the development of this Oracle Fleet.
Pioneer 3 is probably what was upgraded in the Oracle Mothership and allowed it to salvage the rest of the civilization that the Pioneer ships were meant to save. Given Luther's status, it suggests the photoners could be equivalent. Spoilers Dark Falz from PSO2 derive their power. The Dark Falz from Ragol was there for centuries.
One small hitch with that theory. We all know what happened in PSO to the original civilization. Wherein we learn that at some stage they created an AI to renew Coral's environment. This AI was eventually infected by D-Cells and went rogue and killed off 90 percent of culture. Those paying attention will recall that D-Cells, were the actual reason for the Pioneer project in the first place. D-Cells had forced it into Coral, via an asteroid or any such macguffin, and the government wanted to weaponize it.
They put together the Pioneer job to track down the original source of this D-Cells, and found Ragol. Going back to the point, PS0 occurs 100 years after culture gets nuked. Mother Trinity, the rogue AI, was presumably created around the time of these events of PSO or shortly after Episode III. For anybody who doesn't know already, Pioneer 2 flipped Coral the bird at the end of Episode III and colonized Ragol after the total and complete destruction of Dark Falz and Olga Flow following their duel to the death. That is just another narrative thing that runs contrary to PSO2.
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