At least you got a solid answer. I tried calling LG tech support with the exact same type of question "There's a bunch of holes on the back and I have no idea what size screw, or which of the 12 holes is appropriate for wall mounting."
Their response: "We can't tell you anything."
Yes, that was truly their response about it. They didn't know the thread pitch, they didn't know what size screw to use, they didn't know which holes to use. If they did, they weren't going to tell ME how to hang their product. Tell you what, next time I'll recommend that my client buy a Panasonic. Seems to make a lot more sense.