Vref is the 'target speed' at 50' I believe?
I think that is for certification reasons only. In other words the test pilot aims for that as part of the certification process.
For day to day operations the +5 is bled off approaching touch-down (defining "approaching" is a matter of many personal opinions). Touch down is acceptable at minus five from Vref. In practice it is extremely rare to see this as many pilots flare at anything from 5 to 15 knots faster than Vref due lazy flying techniques in calm wind and long runways.