Um, nope. 'Professional' doesn't mean making megabucks on Medium but rather implies industry training and experience. The irony here is that those whose profession is writing do not call themselves 'professional writers' because professionalism is implied, whether you're a novelist, a copywriter, a technical writer, a journalist...
'Professional' is another casualty of the zeitgeist of dumb, much like 'great' and 'honest'.
Here, it's become a bit of a red flag and the quickest way to identify marketers pushing their 'How to make megabucks on Medium' digital snake oil. Don't let the Medium branding fool you, they're not affiliated with the platform either.
The spirit of Napoleon Hill is alive and well, alas.