It's not a bug as such; the server caches every article, and is only updated when an article is edited or on the regular 12 hour cycle, hence why the transclusion wouldn't change instantly. Nocto's edit sent a re-cache request and et voila, the article cached again with the transclusion involved.
It doesn't generally tend to be an issue to be honest, though it does come down to how the MediaWiki framework handles things in general. It's fixed with an easy edit, even if it's a null edit (an edit that changes nothing at all; just edit and publish)