And if you listen to G-Man’s speech, he says, “your hour has come again”. Okay, now that I’m actually thinking about it, parallel reality doesn’t make sense–other characters have reference the Black Mesa incident, and everyone has recognized Gordon.
Which I don’t actually mind, since I’m in the exact same boat my buddy Gordon is right now–last thing he knew, he was put in stasis (teleported?) by this weird alien creature (after apparently being tricked into committing genocide on an entire race and conquering a planet for him), and the next, he’s woken up in some kind of future (parallel?) reality, witnessed horrible things, beaten, and forced (again) to fight and kill for his life, while still having almost no clue as to what’s actually happened. So at this point we (and by “we” I mean “I”) still know next to nothing about what the hell is going on here.