Final answer:
The Walls are portrayed as a perfect family living in Battle Mountain due to the idyllic setting and their harmonious interactions.
Step-by-step explanation:
The Walls appear to be a perfect family in this section of the book due to the description of their ideal living conditions and their harmonious interactions. The text describes the valley where they live as a beautiful and protected place with waterfalls, greenery, and natural caves. The Walls are shown enjoying the scenery and spending time together, appreciating the wonders of nature and each other's company. Their silence during certain moments suggests a deep understanding and connection between them.