I think it's the specific phrasing that becomes problematic. The GP said "can equally be found in China and Indonesia", which means that there are individuals with said diets in the those countries. This is categorically either true or false.

The parent discussed the diet of these huge countries as if they were consistent across all (or even most) individuals. In my opinion, this becomes highly subjective very fast.

Granted, this argument is pretty pedantic, and the threshold which determines when a group is too large to discuss as a single unit is squishy and highly contextual.