there's confusing and contradicting language there but it seems to be based on US data.
here https://en.m.wikipedia.org/wiki/Average_human_height_by_country
... populations of China and India alone are around 170cm on average. I'm too lazy to do the math for the entire world but the two most populous countries by far is a good indicator that the world average should be lower
here https://health.howstuffworks.com/human-body/average-height-for-men.htm
it says the world average is about 171cm