What do you mean with "really" and what do you mean with "mutual" ? In the article, the situation is described where the man in the relationship desires the woman and the woman desires another man. If you're asking "is it always like this?" then answer is simply "No." I don't even think it is very common, but that's judging from anecdotal evidence.

If you would forgive me for being so unromantic on valentine's day, the experience of being in love has similarities to a drug addiction and obsessive compulsive disorder. For most people, such infatuation is short-term, and in long-term romantic relationships usually replaced by feelings similar to friendship and attachment.

In my opinion, fretting over whether your significant other is really as addicted to you as you are to the SO is not productive. Focus on whether you are happy and whether you are getting your needs met in the relationship. If you are not, you are perfectly entitled to do something about it (starting with talking it over). If you are happy and getting your needs met, stop worrying.