I think that's meant in a more specific way and meant to put off Mary Sues.

We all take inspiration and search for explanations, motivations, etc in what we know. In that sense, I too write all my characters based on myself and those around me, as should all writers, really. We are harvesters of reality. (And I pray to god that two of my ex-bfs never, ever read my fic, lololol)