The source of the confusion is the direction from which goblin invasions arrive after they have announced their approach. I've had East and West goblin armies both approach from the left. The goblin tinkerer's comment is just a jab at both the general stupidity of goblins and arguments about where the sun ought to rise and set.
According to the wiki, Goblin armies most often arrive from the left when they say East, so that should be about right.
NINJA EDIT: According to the other wiki east means right, so yeah, wiki fail.
What I was trying to say was that the direction of the sun rising and setting is not an indicator of where east and west are, even though it is correct in this case. (Or not, ninja edit again)
What I was trying to say is, if the game outright tells you where east is, why would you need another source?
Because the game could be wrong!
It isn't in this case, but imagine if some new content appears that indicates the camera as facing north. (A North Pole sign in the background or something. Could fit with the snowy theme, I dunno) Just accepting what the game says because it's a game and set in another world doesn't always work, some concepts are immutable.
I'm going to make a game set on the inside of a hollow planet with gaps so you can see the sun rise and set. That'll show those mapmakers.