Maybe I'm misunderstanding here, but it sounds like he's claiming they invented "interfaces". The Go interfaces seem like the same thing as a Haskell typeclass which predates them by a long shot. Either way a great invention that should be in more languages.
The early days of Go appeared to be the work of a group of people who had not ventured out of their bubble in a very long time and were unaware of several decades of PL research, so it would be somewhat surprising if any of them knew what a typeclass was at the time.
