I know the meaning of zero-slip :)
How does your case look? You know that MRF is an approximation and it might look not really intuitive when it comes to particle tracks. The need to run with relative frame is because espcially for small particles they should not penetrate any walls. However trust-worthy analysis can only be achieved if you run with moving mesh. Let's keep that first aside.
The point properties are relative to the zone motion. You can verify that even without MRF by just injecting from a rotating wall.
The particle tracks (and positions...) that Fluent will calculate and visualise in the rotating reference frame zone will be what an observer sees who is rotating with the shaft / rotor / .... (Think of what a camera "sees" that is attached to the shaft and rotates with it.)
Just create a rotating cell (ring) zone inside a box. The box has 4 sides as pressure outlet. The inner side of the ring is wall and from there particles are injected. The whole ring rotates. Just look there after the particle plots with relative velocity and abolsute velocity to get a better idea what is going on.