The problem with messing around with flaps is selecting the wrong flap setting. Some are electric others are manually operated and the approach should be stabilised.
We use 1.3 times the stall in a given configuration so your stall speed will be different with zero flap to full flap and that needs to be considered.
Also to be considered is more aircraft specific, the type of flap and what settings are drag and what settings are more lift so it really comes down to knowing your aircraft.
If i had an engine failure took full flap and realised I had got it wrong and was going to come down short of my desired spot then sure get rid of that drag no matter whether its from flaps gear speed brakes etc.
I too used that technique of on a short take off leaving the aircraft clean and applying takeoff flap approaching VR. The real danger is missing the flap or taking the wrong degree of flap while your distracted bouncing along a field and really distraction is the key word as your full attention should be on the takeoff not looking down at flap settings
Pace