The PS5 version of Call of Duty: Modern Warfare 2 only has around 70MB of data on its physical disc, rather than the more substantial number of files one would expect from a major game release.
According to MP1st, players who managed to get their hands on physical copies of Call of Duty: Modern Warfare 2 discovered that the discs only contain 70MB of data, which would likely be some sort of activation key and DRM.
Presumably, inserting the disc into a PS5 wouldn’t do much besides prompting the console to download the entirety of the game. Trying to run the disc without downloading anything prompts the player to connect to PlayStation Network to download an update that would allow them to play.
It is also worth noting that players saw a 40GB day one update before they could start playing. Shortly after its day one patch, the total size for Call of Duty: Modern Warfare 2 has grown quite a bit. According to reports, it is now sitting at around 152GB of data.
While there has been no confirmation about whether the Xbox version of the game shares this detail, it would be quite likely that Xbox discs would also similarly include just the license data, rather than a full game that can be played without having to connect to the Internet.