Yes, a single good post could outweigh 1,000 mediocre posts.
Nevertheless, as on *overall/generall/rough* indicator, to be used when analyzing the community as a *whole*, I think the post count is worthwhile.
Posts in the Intro forum are *indirectly* crucial to the site. Greeting someone when they show up opens the door for them to contribute knowledge over the long term. Thus, while the Intro posts aren't *specifically* technical, they contribute to the technical environment over the long term.