Yes. That's exactly the point. If one of them points west, he is telling the truth. If one of them points any other directions then they're a liar. The only way this prompt doesn't work is if one of them knows and lies about knowing and the other actually doesn't know, which is a very hyper-specific circumstance.
FiniteBanjo
You're having a stroke.
I mentioned in the adjacent comment thread that circumstance: if one of them gives a verifiable answer then it is solved, if neither of them know: that requires one of them does know and is lying and one actually doesn't know, which is a very odd stipulation, but you can just ask them any other question with one true answer. "What is 2 + 2?"
Sounds like we're making a lot of modifications to the setting here, but that would require the other guard to also not know because he actually doesn't. If either of them makes a definitive answer which you can then verify, then you can solve it.
This one's the Truthsayer, other one is a liar.
"Which way is west?"
Every time I show up I end up getting myself handed to me by that Dracolich.

The hell is going on inside that head?
I think Game of Thrones had lots of intrigue in the first few episodes but I also didn't like that one because I'm not a big fan of incest, murdering children, discussion of if prostitutes do or do not constitute skill in getting laid, and rape by the ocean. Also, sociopolitical landscapes of medieval Europe in grimdark lack of proper succession contexts.
But I won't judge people who do like it.
An ischemic stroke occurs when the blood supply to part of the brain is blocked or reduced. This prevents brain tissue from getting oxygen and nutrients. Brain cells begin to die in minutes. Another type of stroke is a hemorrhagic stroke. It occurs when a blood vessel in the brain leaks or bursts and causes bleeding in the brain. The blood increases pressure on brain cells and damages them.
A stroke is a medical emergency. It's crucial to get medical treatment right away. Getting emergency medical help quickly can reduce brain damage and other stroke complications.