The Debian project lead, Stefano Zacchiroli, is being terribly misquoted.
The numbers in the article do not address the common case of having one package maintainer for both distros. That 74% actually means that 74% of packages are *in common* between the distros. It is conceivable that much of that 74% is because of maintainers who contribute to both distributions. It isn't fair to say that Debian does all the work and Ubuntu merely takes advantage of it.
Seeing that the same package exists in both Debian and Ubuntu does not mean that the package originated in Debian and was taken without effort by an Ubuntu maintainer. Frequently, the same person creates a package for both. Either by creating an Ubuntu package and verifying that it works on Debian or the other way around.
Go look at the names of package maintainers. You'll see the same big group of people working on both projects.