Kirstey,
Because it is not measured at a point, it does not fit the definition of a QNH which is defined as follows:
The pressure setting which causes the altimeter to read the height above mean sea level of the touchdown on landing, plus the height of the altimeter above the ground.
QFF is the barometric pressure at a stated place, reduced to mean sea level.
A Regional Pressure setting is a QFF not a QNH.
MET.O 630/AP3340 Capt 9.
[ 09 November 2001: Message edited by: Noggin ]