Hi,
I agree with PPRune radar. That's correct. If the acft is cleared to descent to altitude and at the moment is at the FL, QNH may be set as given by ATC if the pilot is not requested to report any FL passing. When is acft airborn and climbing to a FL, pilot is expected to change his altimeter settings from QNH to QNE when passing transition altitude. When passing transition altitude, you are sure you are clear of any obstacle around you.
BRGDS