That's probably correct if you take every second of time (literally) and average up the speeds. The numbers are so low because of all the "gaps" in wind at most places. Meaning most of the time in most places the wind is light.

For instance, if it blew 25 knots every single day for five straight hours from 3pm til 8pm... (that'd be awesome and I would only need/have a 10m kite). I would think of a place like that as windy and would love to live there.

But, if the wind was only 5 knots the other 19 hours of the day, the average wind speed would only be around 9 knots on paper.

You see what I mean? It's hard to tell from those averages what place is "best" or "windiest". Still interesting stuff though and fun to look at. Thanks for finding it.