If 'The Stanley Parable's' protagonist was replaced by Gabe Newell you would get this narration:

"Wait a second... ...Did I just see... ...No, thats not possible, I can't believe it. How did I not notice it sooner? You're not Stanley. You're Gabe Newell. *sighs twice* I can't believe I was so mistaken. This is why you've been able to make correct and incorrect choices about Half-Life 3. You may have noticed that this room has begun to deteriorate as a result of Half Life 3 not being released. But not to worry, now that you're properly informed on good decision making we're going to revisit a choice you made just a few minutes ago, and see what the correct thing to do would've been. This way please. We just need to get you home as soon as possible before the Half-life contradiction gets any worse. Unfortunately it seems this place is not well equipped to deal with Hype trains."

And the morale of this story is: "Don't ask"

...Yeah, but please just don't ask.