Holy shit I made a half-joke about me possibly overanalyzing something and a few days later this is what happens.
people are forgetting that communication is a 2 player game, aka the reader has as much of an say into the story they are perceiving as the writer
Maus Gets a lot if it. Ultimately writing is a conversation, and whether or not the writer had original meaning in what he/she said, the reader gets to define what they think of it. Granted there are such things as wrong interpretations, but if the reader sees something special or different in an entity the writer totally didn't intend for/anticipate, it still is all the more valid.
It makes writing fun! You make your content, pick your meanings (kind of), and throw it out there and let the audience run with it.
tl;dr You don't know that they're trying to be simplistic anymore than we know they're trying to be layered. Plenty of writers do think about this stuff, and do pay attention to what they're writing.
I can see eye-to-eye with you as a writer myself, but I will say that there are often times that I don't put deeper meaning in some things I have written. You don't see anyone dissecting the color of the bedsheets in Madoka or the color of the wallpaper in Toradora, and those two shows are so overflowing with symbols and greater meaning you could write a 50-page thesis on the first 6 episodes alone, each.
In this case, Shou explicitly called to attention the words Keiko had written rather than having her say it herself, or just briefly showing them in passing. There was an allotted upper third given a hefty amount of space in a panel where nothing much else was going on. Enough reason to believe he did want us to notice some meaning in the descriptions.