Control Ultimate Edition, including all the latest expansions is over 50gb so we're unable to fit everything on the Xbox disc. We have used Xbox intelligent delivery to provide some content on the disc and the rest via download.
You can read more about Xbox intelligent delivery here: https://news.xbox.com/en-us/2020/03/16/xbox-series-x-glossary/
On PlayStation 4, this isn't the case as Control Ultimate Edition fits on a single disc, due to compression and other variables.
Once you have downloaded the game, rest assured you do not have to be online to play!