Microsoft might have done away with the mandatory online connection policies, but that doesn't mean that games themselves won't have their own requirements. Forza Motorsports 5 will require a day-one download before gamers can begin playing the game. This basically means that not all of the game is on the disc, and you'll have to connect to the internet in order to download the rest of the game.
Speaking with IGN, Turn 10 Studios boss Dan Greenawalt said that Forza 5 has "required" content that needs to be downloaded in order for the game to be played. This content includes the Drivatar system, and a collection of tracks and cars. Greenawalt says the content is vital to the game's experience and is required for download before you can begin playing the game.
The reason behind the required day-one download comes down to the game's production schedule, and the Turn 10 team is working on the content up until the last minute, which requires that they make the rest of the game available for download online. This means that gamers will need to download the rest of the content that isn't on the disc before they're able to play Forza 5.
However, Microsoft recently confirmed that you'll be able to play games while they're downloading, meaning that you won't need to wait for downloads and installs to finish before you can begin playing them, and the PlayStation 4 has the same functionality as well. So while you'll have to hop online in order to grab the Forza 5 download, you'll be able to begin playing the game while the download finishes.
This shouldn't come as a huge surprise to gamers, though. It's almost a common occurrence when studios delay a game due to production woes or changes in plans. However, with the case of Forza 5, Turn 10 wants to have the game out on Xbox One's launch day, and this requires that they get the disc out ASAP, and have the rest of the content available online for download.