PIC mass inlet in rotating frame

I am testing the new rotating frame feature, this is a great capability! I ran the pic-stir-tank tutorial and I don’t understand how the mass inlet works. Instead of a continuous inlet, I see pulses (roughly one pulse per revolution). I simplified it so there is no initial solids (easier to visualize) and I tracked the number of parcel over time:

Is this the expected behavior?

I also ran a case without the impeller and staying in the inertial frame (no rotation) and I see a continuous injection:

(Note gravity is turned off and there is an outlet at the top of the tank)