It's fair to the extent that you're required to rely on 3rd-party products to get something done. If WordPress-the-Technology uses WordPress-the-Ecosystem as a main selling point, then its their choice to bundle their reputations together.
Interesting concept: reputation bundling. In this instance of the technology and its ecosystem, but potentially useful in describing other situations as well.
Is this something you came up with on the spot? I haven't come across this idea in communications literature and a cursory search only brings up other types of bundling in economics/business/strategy.
