The goal is to write things that come from the heart as well as the brain, that leverage your passions and appeal to an audience, all at the same time. In other words, the goal is, as usual, somewhere in the middle.
If your starting point is that you think nothing of your own passions, interests, and write whatever you think will please an audience, then yes, this advice is right on the ball for you: you should write for you, because it's about you.
If, on the other hand, your tendency is to boldly write what you care about, following your passions and interests and not giving the audience much of a second thought, then the opposite advice applies: write for your audience - because it's about them, not you.
Of course, "write for both the audience and yourself" doesn't make such a good sound bite...
I'm reminded of a quote, by Niels Bohr, I thin, which said that the opposite of a Deep Truth is another Deep Truth...