@Blahbs I don't think Yukisuna is saying she's short !
The problem isn't her height, it's her weight. She's not small, she's rather tall, 166cm is above the average Korean woman height but with that size 40kg is far, very far from being healthy. 166cm 40 kg gives you a 14.5 BMI. The WHO considers for asian population a BMI < 18.5 = underweight, ≤ 16.5 severely underweight, ≤ 14.5 life threatening.
So either the author "has no understanding of proportions and realistic female body weight" as Yukisuna said or the author is trying to suggest hunger, malnutrition are common in this world.