I believe the concept of a "trial edit or project" exists as a complete logical fallacy. Think about this- in the hopes of finding the best fit for the job, you shortlist the best editors and production professionals you can find and offer them a beyond discounted rate (or sometimes no money at all) to assess the quality of their work. You're asking someone to produce their best work with little to no incentive and with a budget that doesn't allow them to dedicate their full focus on it.
I don't know of any industry outside of the creative industry that allows this as a common business practice. This is not the industry where resumes matter. Only portfolios and I guess customer reviews hold any weight. If my portfolio isn't enough proof that I'm good at what I do, no trial project will ever be worth the time.