You guys are both arguing against different arguments.
Hmm, Vietnam and Peru might not have been my best choices here, but I still don't think the averages would stay around 5'4 with decent diets and proper sanitation.
I'll help you all out here.
Here is an infographic on Japan's average height over a bit over a century. Japan is a developed nation.
There was a continuous increase in height, associated with better diets, hygiene, and healthcare since at least the 1890s. However, it stabilized in the late 70s. The average Japanese man stayed around 170~174cm (5'7~5'8.5). They didn't keep the same pace, in terms of average stature growth, over the last 40 years. This is almost certainly because of genetics. Japan doesn't require better sanitation, the country has a pretty carnivorous diet, and children are even given milk at schools every week, despite the low lactose tolerance in the population.
Here are the two main papers that cover our present scientific knowledge of height and genetics:
https://www.nature.com/articles/ng.3097https://www.nature.com/articles/nature21039As it stands, we still know very little about all the genetic factors that govern height. However, that does not mean it's not of the main factors that could define an expected height range in adults.