I could name a non-Steam game "Eternal Crusade" right now if I wanted. So, if I may quote Gabriel, one of the few Mon'Keigh who aren't horribly incompetent: "Such are the ways of Daemons; to lie and mislead us!"
Damn you date ayjoi the weboo damn you to hell And then to the warp so slaanesh may violate you and khorne can use your blood on his cereal he is advertising tznech may use your skin as normal birds use news paper and nurgle gives you space AIDs. I will personally my self IRL drown you in DA DAKKA for this taunting insalt AND in stilling false hope and rage into my soul so beware for this community as a whole will hunt you down and kill you and chaos players will use your blood to paint their models that follow corn- I mean khorne. You will be drowned in actual Dakka. THIS IS A PROMISE!!!!!
It's pretty easy to fake, though closed alpha invites tend to go out a lot earlier than most people realize. They're usually pretty hush hush so who knows.
fyi, you can have an application with a name of your choosing and then add it to Steam so it shows as a non-steam game. What is in the image can be anything. It could even be that 2-week build that the team made a video of, or just some random application to get a cool screen shot going that would make everybody jump.
This would be cool if true, but it's very possible he just renamed a shortcut to that specific title you see in the screenshot. Not sure.