It's much more nuanced than that.

Bread and water is prisoner food, but avocado toast and cream-cheese bagels at the corner bodega are considered mid-to-upper-class fare. Pasta (also wheat) can range from kraft mac-and-cheese (poor-coded) to hand-made pasta with pesto sauce.

Rice and tea (ochazuke) is historically the "bread and water" equivalent in Japan, but people of every socioeconomic class still eat rice and miso soup for breakfast, eat rice balls (onigiri) regularly, and generally eat a diet with a lot of rice.

Even though rice is the staple food of Japan, I'd actually argue that instant ramen is much more poor-coded these days than even ochazuke.

I wouldn't be surprised if the middle class and lower class eat more-or-less identical quantities of rice.