I'm sure what you say is true, but here's the thing... you know what that makes you? An exception. And as a first pass heuristic, "don't bet on exceptions" is a pretty reasonable guideline.
Trick is, i never found out how to go beyond Upwork. I never, ever made a good deal with anyone outside of it. It gets me super concerned because i'm locked into one platform, but have no idea what to do.
Not to jump on the original point of this article, but I would suggest creating a personal blog, professional LinkedIn profile, and a technical focused Twitter account.
The reason you can't make a deal outside Upwork is that all of your information that would cause someone to trust you is on Upwork, and only clients using that platform will see it.