In the case of our airplane (CRJ200), the thrust is brought to idle at 50' AGL.
That sounds pretty unusual and rather prescriptive imho. Is that the manufacturers advice or company SOP? What speed target do you use for 50'AGL? If Vref +5 then the flare process will surely result in touchdown at Vref minus quite a few knots. What happens in windshear, do you still retard the levers at 50'?
I fly the B747-400 and have flown B737's and A320 family, and even in the B747 I would not dream of reducing thrust in normal circumstances until about 30' AGL, and the 747 because of its mass carries much more momentum than any of the other types I have flown, and doubtless MUCH more than the CRJ200.