The distinction from a discount matters. When mentoring is made affordable by asking mentors to lower their rate, the pool of available mentors narrows to those who can afford to work below market — which is not the same pool as the best mentors.
Sponsorship moves the subsidy to the party that chose to fund it. The sponsor is buying an outcome for a population it cares about, and the price of that outcome is the mentor's actual rate. It is the only structure in which a programme can recruit mentors on quality rather than on generosity.
Sponsors ask for reporting, because they answer to their own funders or their own board. A seat that produces no outcome data is a seat that does not get renewed, which makes progress tracking part of the funding mechanism rather than an add-on.
Mentor10
Partner organisations on Mentor10 fund seats, assign mentees and receive programme-level impact reporting, without touching the rates mentors set. Mentors are paid in full.