To start:

The overarching theme of the franchise is free will vs control. This theme was established in AC2 but lore-wise it all started with Adam/Eve and other humans rebelling against the Isu during the First Civilization.

Throughout history there has always been a faction that wants to control humanity and that faction has always changed over history: Isu>Cult of Kosmos>Ancinet order>Templar’s>Abstergo. All led by different people, but same goal in mind.

So to answer your question, the significance is that Odyssey shows just how far this war has raged on for. Odyssey isn’t really what I’d call an origin for Templar Order. Just another piece of the puzzle and keeps the overall theme consistent.

Oh and how the Isu, a long forgotten sort of dead pantheon of superhumans, are the ones still pulling the strings.

I ramble a lot. So I hope I answered the question and shed some additional light.