Step
Okay, opening my mind...
Can anyone present any authoritative training document, standard, or aircraft normal procedure, which describes retracting flaps for a continued approach in a powered GA plane?
Test pilots and flight standards people develop and approve operating techniques for aircraft. Is anyone aware this has been done for this technique?
Is it trained anywhere in formal flight training?
Are there stated limitations or guidance as to when to do it and when not?
But you are not opening your mind, you are closing it off to any answer that has not already been provided by authority. So let's turn the question around and ask where is it forbidden for flaps to be raised from 30 to 20 above 400' in a C172? Nowhere. And yet there are plenty of references to not reducing flap on 'final'. So where do you draw the line? As long as you are legal and flying within the limits of the aircraft you decide for yourself; that is why it is called a licence and why you have the discretion to do things that some other pilots would consider unwise:
As the carb heat begins to have an effect, consider flying at a reduced power setting (and leaning more if need be), as less volume of air going through the carb at the lower power setting needs less total heat to warm it and melt ice.
...being a case in point.