[2021] An update of 66 gigs downloaded on first run -- what is this?

I purchased both Odyssey and Valhalla through Epic, and on first run the ubisoft connect app downloads a mega update, 66 gigs. Why is this needed when I just downloaded the full game from Epic? What can you possibly add that's not included in the Epic installer? And if it's vital data to run the game why do you deliberately omit it from the Epic installer? This is outrageous, a waste of my bandwidth and time. Please respond at your earliest convenience and explain this policy. Thank you.