I still think it's very good advice. Barely anyone bothers to share their knowledge, and even less people manage to communicate it effectively. In this context, if you put any amount of effort into sharing, you're probably already "the only" among your close peers.
Just because you're "the only" doesn't mean you're the smartest person in the room. You might, however, have the knowledge in the right areas that makes you indispensable. For example, I often find myself to be the only person around with enough knowledge in the areas of graphics, design and programming to combine them effectively. I might not even be particularly talented in any of them, but very often I'll be the only person capable of knowing how to complete certain tasks.
Just because you're "the only" doesn't mean you're the smartest person in the room. You might, however, have the knowledge in the right areas that makes you indispensable. For example, I often find myself to be the only person around with enough knowledge in the areas of graphics, design and programming to combine them effectively. I might not even be particularly talented in any of them, but very often I'll be the only person capable of knowing how to complete certain tasks.