Most manufacturer's POH landing performance tables assume throttle off at 50 feet. This is perfectly safe providing the correct airspeed is attained at that point. Leaving partial power into the flare in order to attain a smooth touchdown has its drawbacks - primarily the elevators are very sensitive due to the slipstream effect and thus a balloon may occur and also the extended float is undesirable.
Unless the manufacturer's POH states otherwise, the throttle should be fully closed as the aircraft is flared for landing. This is especially important if the idle RPM is found to be higher than the POH figure during engine run up before departure. This is because high idle RPM leads to the problems described above. Record the defect in the maintenance document.