I believe the Android team members at least have always favored Intellij based on the comments I've seen praising it in the Twitter Feeds prior to Android Studio's announcement and also that it's always been supported along side Eclipse as a way to easily import the AOSP source into an IDE (though only if you look in the source itself) if you choose to do so.
In this case, though, it looks like Jetbrains wrote a plug-in for PHPStorm, and Google is just mentioning it as a good method.