The last time I was looking at contracting I was negotiating $100+/hr contracts through Upwork. I had high leverage and negotiating power whereas gig jobs do not. I also had recourse for stuff like what happened here as long as I worked it into the contract I was signing, again not something you get in a gig job.
For 12.5 grand my next words to Upwork would have been, "My lawyer" and if that didn't make any headway I'd be going after "Robin" in court too. These are not avenues that a typical gig job have either because the amount of money doesn't make it worth it or their contracts which are created by the company don't give them the option.