It may not look good on the surface. From what I understand their solution was to limit the amount of overtime hours and used the money they were paying in overtime to increase everyone's regular hourly. Everyone is still getting regular hours. Employers are required to pay overtime but they are not required to provide overtime hours. If the employees don't like how they run their campaign they can find other jobs.
But yeah, the fact that they weren't paying $15 an hour to everyone while promoting a $15 hour minimum wage is hypocritical. Even if they say they were paying what the law states they should pay they should set the example if they want to really effect the change they want to see.