Having flown both Boeing and Airbus, here is my observation.
Airbus have a simple flap selection naming process, in that the flap angle is really irrelevant when flying. Boeing have traditionally named their flaps corresponding with their angular position.
Flap 2 drives the slats out to their intermediate position with no obvious change in aircraft attitude, but as the trailing edge drives out from the fully retracted position to the intermediate position there is a signifiicant increase in the wing area and thus from first principles a significant increase in lift and change in the centre of pressure. Thus the balloon.
It has always been my belief that Boeing overcame the ballooning effect by have lots of intermediate flap settings to minimise the balloon effect.
Having flown Fokker 50, BAe146, 737 and A320 the 737 was the only one that didn't significantly balloon at intermediate flap. But then the B737 has flap 1, 2, 5, 10, 15, 25, 30 and 40.
The ying and yang of aviation.