Eh if that's reflective of China's actual proportions idk if I would call that biased. If 33% of China's population resides in an area then I would expect 33% of people surveyed to be from that area. Anything else imo would be biased in the other direction unless the rural responses somehow had less weight in the final conclusion to compensate. That (the electoral college, that is, which does exactly that - give the rural minority disproportionate voting power) is how we got to the situation you're describing in the USA.
Eh if that's reflective of China's actual proportions idk if I would call that biased. If 33% of China's population resides in an area then I would expect 33% of people surveyed to be from that area. Anything else imo would be biased in the other direction unless the rural responses somehow had less weight in the final conclusion to compensate. That (the electoral college, that is, which does exactly that - give the rural minority disproportionate voting power) is how we got to the situation you're describing in the USA.