Okay, I’ve seen this argument before and I personally find it weak to be honest.
(Note: reading this over, it sounds a lot more hostile than I meant it to be, sorry, tone down the vitriol a tad when you actually read it)
The “make it up as we go” thing is an out for VALVE to get away with inconsistencies, it’s not a license to outright dismiss any inconsistency. Everything is pretty much canon until Valve says “sorry about that” in an interview or it’s directly contradicted in a game (i.e. in Ep 1 Gordon goes left but they decide for story reasons he really went right in Ep 3 to use a weak nonsensical example). Everything the G-man did is part of his personality, actions, and current motives. Even if it wasn’t originally meant to hint at a certain thing it has to be worked into the new story unless Valve handwaves it themselves, you can’t just say “well, Valve makes it up so THERE.” It’s a tool so they can say “he was lying because we wrote ourselves into a hole otherwise” not “well, we make it up so you can’t take anything as evidence of someone’s motives.”