I think I know what happened here. This guy who wrote these articles is referring to Vocal Media. Vocal Media has a minimum of 600 words. Vocal Media pays you more if you're a paid member. I don't know if they allow series, but they are a popular place for fiction - they run competitions including fiction, and I think fiction might do better than non-fiction. To me, I think he wrote it about Vocal Media and just repurposed his article for Medium, without changing the content much. That's stupid, frankly.