It is true !
Both ancient history, modern history (UK colonial office surveys, what surveys the older Afghan governments could cobble together, Soviet surveys & recently (last 10 years) a USGS survey all confirm. Recent Chinese surveys (which I know the least about!) again confirm.
You have to have a stable society to take advantage of it.
If you can’t take advantage of it, it doesn’t matter if you have it.
Again not advocating we stay!
Mexico is a stable country and they have MUCH in the way of raw materials. Yet, the people generally are poor. The relatively few wealthy families own the bank$, land, military and police. Their leaders, of course, come from those families.
There are exceptions...but not many.
They are an Afghanistan of North, Central and South America.
It makes me EXTREMELY grateful to live here. HOW BLESSED we are!