Denti,
I wrote if you follow the glide path (Ils), at a preset path angle, in a B737 you will see 3 reds and one white as the papis angle is set for larger aircrafts.
If you decide to follow the papis when visual (lets say from 500 feet to threshold) and go for 2 white/2 red your aircraft will be maybe about 80 feet above threshold rather than the usual 50 ft.
Ducking below the glide in the last hundred feet (ie trying to make a short landing),you will as you said make a longer landing as the flare will be increased...hence your QAR readings.