If you buy Call of Duty: Infinite Warfare on the Windows 10 Store, you won’t be able to connect to anyone who plays the game through Steam. This means that the playerbase will be limited to anyone else who buys it on the Windows 10 Store, severely limiting how many people you’ll be able to play the game with in multiplayer.
Given that Steam is the much more popular platform, you’ll definitely want to get the game on Steam if you intend to play it online. Furthermore, all boxed copies of the PC game connect to Steam.
This little detail was revealed on the Windows 10 FAQ at Activision Support.
It’s puzzling as to why Activision or Microsoft created this barrier between Windows 10 Store purchases and Steam. Hopefully it’ll be rectified before the game’s release, if not shortly after—or anyone who buys the game on there won’t be able to play with all that many people.
In the end, it’s the consumer who gets the short end of the stick with decisions like these.