It was like that last week when I pre ordered too, then it changed to steam play. The beta still isn't up so my guess is they are having massive problems with everything, people were able to play the beta already on mac so it is playable.The game was widely advertised as being created for both Windows and OS X, including during the pre-release promotion - but to my surprise, the Steam store now display only the Windows icon. What the heck is that?
They've just messed something up on the store and it's getting added in/fixed before release.No, it is not. Try visiting the Steam Store and look for the game there.