That's what I meant by them covering SRW A. If you look closely enough you'll see not only the Angelg but also the Soulgain. Those are the two primary mechs of the original protagonists of SRW A, Lamia Loveless and Axel Almer. The plot of A had Axel lose his memory before the events of the game, hence his protag status in A, OGSaga EF Exceed, and now most likely this game OGs2.
Although if I'm remembering A correctly, they've already covered those events in OG2, so they may just be there as part of OGs2's contributions to the plot instead.