I'm pretty sure this contains all the multiplayer modes like Warzone, which are separately installable, and contain a lot of content from previous games. If you just install the parts you play, it should be a lot smaller. I'd also expect they'll probably slim down the game size on Switch 2 anyway, both due to lower quality assets than Series X/PS5, but also potentially removing that content from the previous titles in the series, as they're not on the console. I don't play CoD games, though, so I'll admit I'm not 100% sure how it works.