From what I have read from the community posts (and from my own personal experience), this achievement is pretty bugged since the 1.5 update and may be difficult to trigger. It will likely take a few attempts.
The methodology I used to finally get this achievement to trigger was repeating 72's dreamscape by going to the alter and sitting through all the dialogue again. *DO NOT FINISH 72 LAST* as doing so will send you to the next segment of the game and make interacting with these alters no longer possible. Otherwise you will have to clear your save and try again.
If repeating the alter and dialogue doesn't trigger the achievement, then try closing the game and starting it up again. This is what triggered it for me (I also transitioned to windowed instead of fullscreen and used the cheats to save time)
Also some helpful time saving cheats:
R_SHIFT + 'G' = Gun
R_SHIFT + SPACE = +15 sec