It is actually slightly more confusing than Noggin would have you believe. The Regional Pressure Setting is, in fact the lowest forecast QNH (Observed pressure reduced to sea level using the International Standard Atmosphere) in a particular Altimeter Setting Region. The forecast is made 1 hour ahead and is valid for 1 hour (e.g. the forecast for 1200-1300 is made at 1100).
The fact that the RPS is based on the lowest forecast QNH probably accounts for the misquoted 'Regional QNH'. As to why the incorrect terminology appears in licence examinations - best ask the supposed experts at the CAA who set the exams!