Posted on Discussion section but no one seemed to care (and that section feels more for casual talks).
Some articles (e.g. acecombat.fandom.com/wiki/Wit) state that the Sol2 to 5 joined the old VAF before the annexation. But the a Reference used (https://ace7.acecombat.jp/clm/column03.php) only says Wit and the rest were "born in Voslage" and "participated in resurrection activities"(obviously after Farbanti).
Plus DGDrocks7 mentioned in comment of Wit's article that Wit said "his generation can no longer speak Voslagian" during the cutscene, wouldn't this makes them born after the annexation and no way to join the old VAF?