Is this a Steam AR game to promote The Witness?

Steam sleuths have reportedly found what may be another of Valve's AR games.

Something mysterious has turned up, spanning multiple games on Steam and dating back to May 2015.

According to a summary post on /r/GameDetectives, clues have been found in Mini Metro and The Magic Circle, among other games. Here's what's been found so far:

• A secret map was added to Mini Metro in February 2015, which when solved rewards the player with a strange sign (the "sigil" or "eye", pictured below)and a a mysterious set of symbols.
• An image was added to Crypt of the Necrodancer in May 2015. Hex editing revealed the same sign as that found in Mini Metro, along with another set of symbols.
• The sigil also appears in Legend of Dungeon, yielding yet another set of symbols.
• The sigil is also found in The Magic Circle, although nobody knows how long it's been there or how to make it give up another set of symbols.

Making it all a bit more mysterious, the sigil is also found in web game The Kingdom of Loathing, which casts a bit of doubt on whether we're looking at a Valve-created AR game or something else entirely - maybe a collaboration among indie developers.

I gotta say, assuming this is all legit: it feels like something to do with The Witness, which is full of symbols similar to those being revealed through this AR game.

It may be some form of promotion for the game, since it releases this very week, but I wonder if it might be a meta-puzzle. Jonathan Blow said The Witness features some puzzles almost nobody will solve.