I think it very much depends on the type of aircraft flown. I used to teach it on some types where the first stage of flap was a relatively small deflection but gave a lower nose attitude thereby improving the view for the turn from downwind to finals. Also, the reduced speed makes for a tighter radius of turn thus allowing a lesser bank angle for the same rate of change and the increase in spanwise flow associated with flap application improves aileron effectiveness on most types.
All in all I would say that it is a valid procedure if it fits for the aircraft you usually fly.