Shirren - is the Battle Cast that Wren was model after during the War. In the Original JP version of III it had been mess up with part's of it's story and later they tried to fix it as best as the could with later version's. But Sega goofed up by forgetting to add in his name and leaving it Shirren since he was a Copy of the Original Shirren and actually TYPE #386. In one version it has only #386 and in the Original JP version Wren call him self that in-game and not Shirren. And if you take it into the count that the Original US version of III calls him Wren and not Shirren which was only 1-2 month/s behind the JP one. With the Producer saying there were mistakes and some they couldn't fix. The time period's listed in both, Wren's knowledge of III in IV. And how & why the Differences in Wren's bodies is pretty easy to follow (Technically Barrier is a Tech in IV).
One thing you also realize is that Shirren was built by Orakio along with Miun with a soul purpose to be generals for the Orakian & Layan War. This is year's (5-10yrs.) after Exodus of Palma. And it's not 1K years but 100yrs. form Rhys since it was another mistake in the coding which they tried to fix in the US version. So taking this here, there would be no way for the people of Motavia to have that Tech unless that World ship in Orbit around the planet was Alisa III and Crashed on the Planet. Then the Motavia's had the chance to rebuild & re-purposed him in the same amount of time in PSIV using the Tech (the best they could) form Alisa III's rubble (this was also done with one of the Lou copy bot's in PSU Ep.3). Oh, Sean's Time line make's this possible in PSIII.
Another reason is that Wren built Demi and not the Motavian's since they couldn't do it from scratch. And Wren was the only one who had that knowledge (he's also the one who fixed Mieu in PSIII).
I could go on and on. But I think you can see where I'am getting at with this. And the Best thing is One could finally connect the full series together which is another Plus.
Updated: Anna_Wren - them being classmates was to establish a time point where Orakio came from, even tho he was an engineer didn't built anyone until after the Palma's demise. Wren was never built before MB demise since there's proof that Alisa III leaving before MB and Palma being destroyed. That mean's Palma & MB had time to build the world ship's before the end and giving MB and the Earthmen ample time to sneak in Falz's on each ship. And this was during Rolf's quest and during his Jailed time before his Escape form the satellite, almost 2 yrs. worth according to PSIV. And according to Wren himself in PSIV he said that the Motavian's didn't purpose him until about half a millennium after Palma's demise, shortly after? unless you think being on a ship for about 500 yrs is being short.
In light PSIII is a filer story of what happen's to some of that last 10% of Palman's after the demise of there planet, for the next 500 year's or 5 (3 starting from Rhys) generations. Between the event's of PSII & PSIV which is only 1,ooo yrs. apart.