The issue with reports saying tall men get paid more is somewhat biased if you're looking on a global scale. For example, Asians are smaller than most, we'd all agree on that. You'd only find low paying jobs like sweat factory wages in Asia. Things like that tip the scales big time.

Also, there most likely isn't a causal effect between height and pay rates, but rather "what's causing the height" vs pay rates. We know that the average height of humans have increased over the last century due to things like better nutrition, public hygiene, etc. (America experienced their first drop in average height a few years back. Blame junk food). So in that regard, it's more likely a person isn't earning as much as others because of other factors, such as poor family background, malnutrition, lack of education.....all those lifestyle things that limit their opportunities in life, as well as height.

Of course, they could do localised studies in certain areas to make it more localised, but they'll still never eliminate all other possibilities and keep the only variable control as height. I think demographic is more of an issue.