I'm pretty sure it's only on Xbox/Microsoft games... like Quantum Break and the like. Either first party games and/or the ones they have deals with for timed exclusives, like the new Tomb Raider.
I don't think this will work with multiplatform games like say Battlefield, Call of Duty, Fallout, Mass Effect, Final Fantasy XV etc, etc..
So it's like saying if you buy the Xbox version you'll get the PC version as well. I'm not sure it's the other way around either. Or if it is, it's not universal. I.E... if I buy Quantum Break on Steam or something like that (if I can even) then I won't get a copy attached to an Xbox Live account. I'm not even sure if you buy it from Windows Store that you get the Xbox version digitally. They should do it that way.
Overall for Xbox One owners it's a nice gesture because they don't have to decide between playing with their friends or some convenience factor (for those that don't hook up a PC to a HDTV/4ktv like they do their console and use a controller with wireless kb+m) or getting the more advanced PC version. It's almost like getting the 'remastered' version for free and five or so years early.
What it also showcases is that Microsoft desperately wants to keep people in their ecosystem. They realize many people won't buy an Xbox One because the PS4 and PC is/can be more powerful, and many people have already jumped to that and aren't looking back.
This way Microsoft can not only promote Windows 10 and get more people to upgrade/buy Windows 10, but it also creates a situation where you are still in their ecosystem.
Because there is little point in me buying an Xbox One, having a PS4/Wii U/PC... having the games on PC allows me to keep current and come back to the fold in a way that helps me keep familiar with their IP's. That way, when the Xbox Two or whatever comes out, I and all those like me are not out of touch with Microsoft and their games/services so I will be more likely to want to purchase an Xbox Two.
It's all about not pushing customers away. Microsoft wins whether you play on Xbox One or Windows 10, and they want to keep that going. They really want people to use Windows Store like Xbox gamers use the Xbox Live store.
I also second the notion that it helps the studios that can now develop either a Microsoft only game, or a timed exclusive. Tomb Raider was a debacle, because 2/3rd to 3/4ths of the audience couldn't play it. Plus they launched it on the same day as Fallout 4, and right after Halo 5 and Call of Duty BLOPS3 and just before Battlefront. Sure they got money, but the downside was, now they are going to get tanked on PS4 sales for the game. Few are going to buy the PS4 version a year late for $60 when you'll be able to buy the game on PC for $20 (or less) and Xbox One version for a similar amount. Few might be a wrong word. A lot less then it would of have been is more accurate.
By going to a PC/Xbox One model they increase that share of games to better compete against PS4 only games.
It's smart. Instead of being pig headed and lose, because they are, they are making things more consumer friendly in the best hopes of securing your business long term. I applaud MS for taking this much smarter approach.
