Transmission noise - DualMass or Throwout?

[S.hafsmo]

On a recent test drive I heard a rather disturbing noise coming from the transmission when the clutch is depressed, and the input shaft has a higher speed than the motor/flywheel.

If I just depress the clutch, there is no noise, but if I rev slightly in neural, clutch enganged, then depress the clutch, a loud rattling/grinding noise appears, and continues until clutch is engaged again.

If it was the throw-out bearing, would it not make noise every time clutch is depressed? Is my dual mass flywheel failing?

A quick and rather poor video of the noise; https://youtu.be/yHi75CXl2lM