No, I mean exactly what you described (you can blame my English).
Yes, the water flows but from the propeller backwards. The boat doesn't move so there is no flow from the skeg (which is in front of the prop) towards the prop. So, with the "basin trial" I still have a running engine, a rotating propeller in high rpm that would "normally" cause vibrations but have eliminated the movement of the boat. Result, no vibrations!
