Because the links on there were dead:

• https://en.wikipedia.org/wiki/Blackbird_(land_yacht)
• archive.org – http://www.fasterthanthewind.org
• A Long, Strange Trip Downwind Faster Than the Wind – Wired 08.27.10
• Wind-Powered Vehicle Can Also Travel Upwind Faster than the Wind – Wired 07.11.12

I’m no sailing expert, but I recall the same can happen when you are running (point of sail).

I wonder why this is not used on sailboats or ships.