I'm not going to argue whether his numbers are wrong or right, but I think his definition of the "Linux ecosystem" is wrong. I would say that all the free software that's included in the various distributions repositories are part of the Linux ecosystem.
Canonical has clearly focused a lot on the desktop (where Redhat and Novell have been more focused on the server side), particularly a desktop based on Gnome and they have no doubt been pretty succesful in that regard. A lot of what they have done is polish and making things "just work", stuff that I think can be hard to measure.
To get a better picture of how much or how little Canonical have contributed to the ecosystem, you need to include all the software that's part of Ubuntu.
Canonical isn't exactly a big company so there are limits as to how much they can contribute. I think part of the reason they are in focus is because they have been quite succesful on the desktop and gotten a lot of users. Would the critic be different if it was for example Slackware?