While completely agreeing with the premise of that the article is purely to drum up traffic, there's also some truth in it.

Ultimate Caveat: In my experience...

I've rarely been able to put my hand on my heart and recommend/use WordPress for larger projects; in part due to it's reliance on a small "core" community (there are of course many other issues).

While WordPress has an exceptionally large userbase, my experience is that number is almost always skewed by "WordPress.com". Which is not to say it's not a huge number, it's just to say that it's not as big as people make out.

The opposite of that though is the central/trusted community (I'm trying to avoid the word core). WordPress has a greater number of fanboys ready to "drink the kool aid", and it's current release cycle is difficult for casual contributors (theme, plug-in, core, forum support) to keep up with.

Drupal and Joomla on the other hand have a very different type of community, that on the outside appears to be lacking in some of the basic processes and metrics that the WP community has gotten used to. But when dealing with sites larger than "Blogs with some static pages" or with large amounts of data-utilisation/complexity actually getting answers to in-depth technical questions is considerably easier with both Drupal and Joomla communities.

Much like your plug-in post, it's less about the numbers and more about the quality/responsiveness of the community. Personally, I find the quality/responsiveness of the WordPress community very high in the centre, but drops very quickly. Drupal and Joomla have a slightly better curve on their community.