"Why are the ribs so expensive?" marked wrong. I know this is a Korean test, so maybe the word "galbi" is preferred, but there is absolutely no consistency about this - sometimes a direct reproduction of the Korean term is okay, sometimes a translation is preferred, and there is never any method for knowing which is going to be expected.
There are massive issues with equivalent English sentences being accepted, but I don't think this is an issue. Food names at a Korean restaurant are not generally translated into English. Calling kalbi/galbi "ribs" would be almost as awkward as calling tofu "bean curd".
I agree with your first point, but not that this in particular is not an issue.
Food names are not generally translated into English? Perhaps in Korea but would argue otherwise for other countries.
Your point about 갈비 being akwardly translated compared to tofu and bean curd would be applicable happen the English language didnt adopt such words, including ramen and sushi, plus more - these are found in the English Oxford Dictionary.
If you took your friend to an Asian restaurant and asked them if they wanted tofu, sushi, ramen or galbi, most likely they would understand three of the four and ask "what is galbi?"
As such, and until galbi is adopted into the English language, a more natural translation is in order.
In guessing this is because it was the work of multiple people, but i agree that there should be more consistency