The G reading recorded on a TP is a normalised value with a combination of aircraft weight and deceleration in the Z axis. Which then spits out a value which can be graded by the gingers.
Having been on a Q400 when its done a normalised 1.8g landing it hit very very hard.
BTW I agree with MM its usually people prolonging the flare and trying to do a greaser which is when they occur. The aircraft runs out of energy and drops out the sky.