I'm trying to figure out what I'm missing here. Why would anyone want to bring their clients, who pay them directly, to Upwork, where they would have to pay a 20% commission?
I would like to clarify that the Bring Your Own Client program allows you to bring a client to Upwork. Contracts with clients who are brought in through this program will be charged 0% Freelancer Service Fees. That's 0% on all contracts you have with that client, forever. Even if you lose your Top Rated status, you’ll continue to pay a 0% fee on these contracts. You may read more about it here.