That is true, although the valets still accept tips.
Some people think it is a 'perk' for being handicapped, but it actually is because much of the parking at the resorts is too far away to meet the guidelines/requirements for handicapped parking. In order to avoid having the entry areas to the resorts full of handicapped parking spaces, resorts offer free handicapped valet parking as an alternative. That is not just for WDW, most large hotels do the same thing.