It also seems that he didn't look at an operating system, but instead looked at a much bigger thing: everything packaged by Ubuntu. So GNU's contribution is watered down by counting 20 IRC clients and a load of software that most people will never install.
And that's ignoring the infrastructure work done by GNU - software, organisational, and legal. Who produced the licences? Who made the development tools so that other developers could write other parts of the system? Who set up a charity to pay people to work on the necessary system components? Who raised awareness of the importance of working on all this? Who worked on essays about policy and philosophy?