Both xbox and Sony let third parties sell digital keys for a while now (year+), amazon has been selling them for a while and even matches weekly and flash PSN/xbox sales and of course amazon owns Twitch so the infrastructure is all in place. You get a key you redeem on your console (or the console website). I bought a few that way, they are the exact same keys as if you bought directly from Sony or Microsoft.
I just hope this encourages more digital discounts, even to this day its normal to see new games go on 30-50% sale within a month but very rare to see the digital code go on sale. Heck, with amazon prime you can buy a new physical game for 20% off for 2 weeks, but I doubt that will apply to these digital codes.
End of the day this doesn't seem like that big a deal, its $3 to the streamer on a $60 game. I don't see hundreds of people buying games per month per channel, a big chunk of the audience are people who just don't play the game but just want to see it and more importantly feel like they are in a social environment while doing something else.
