during flap retraction one is flying below flaps maneuvring speeds for the new flapsetting as next flapsetting is set at the current flap maneuvering speed
The thing some people seem to miss is that the FCTM states -
"
With airspeed increasing (my italics), subsequent flap retractions should be initiated:
* when airpeed reaches the maneuvering speed (number) for the existing flap position."
With increasing airspeed, the time you are exposed to any reduced maneuver margins during flap retraction, is quite small. However, I see a lot of pilots calling for flap retraction without a speed trend vector i.e. stagnant airspeed.