I haven't read the paper but do they define what they mean by "westernized"? China is very much the east, does acne vulgaris have the same prevelance in countries in Asia and the middle east?
The speculation is that low-glycemic load diets are related, possibly through insulin sensitivity/resistance. So probably an industrialized Chinese diet with a relatively high proportion of refined rice (or other grains) is also prone to acne.
I'd say there are plenty of western/Western attributes that could have a cumulative (?) impact.