There's no reason for him to change his guide. He gives good explanations on how to get each achievement and in his roadmap lists each achievement that is missable and gives a brief explanation on how to get it. Compared to many guides that I have used on here that is a huge advantage, as most just say that there are missable achievements (sometimes how many) but not actually which ones are missable. You can then use this information to look up the achievements in the guide.
This leaves two points of view on achievement hunting:
First that you play the game to get the achievements
or Second you play the game to enjoy it and then finish up any achievements.
Most people in the First group (which it sounds like you are) would read through the entire guide before starting the game and set up a plan, or at least get an idea, on how to get the achievements. While the second would play the game blind first and then do the same.
As for the walkthroughs, I assume you are talking about tastefulmrship's walkthroughs, where right at the beginning he says that the walkthrough will get you the achievements, but you will miss between 25-50% of the game. The quote is from his intro to the Episode 1 walkthrough
Originally Posted by tastefulmrship
I can't be held accountable for the results! This walkthrough is set out exactly how I did it, it does work! HONEST!
If you follow this walkthrough as it is you will get all 12 achievements in the correct order, however you will have experienced about 75% of the game and well under 50% of the conversations (256 on the leaderboard).
I should also note that the achievement hunting styles I listed earlier assume that you are going for all the achievements and that you either want a blind (no previous knowledge generally for enjoyment) or achievement maximization first playthrough.