Hi Aviator_8998
“After rotation, passing 10 degrees of pitch attitude, extra backward pressure is required to continue rotation to the target pitch attitude.”
That effect is due to the proximity of the tail to the runway. Around 10 degrees of pitch, the airflow felt by the tail is parallel to the runway surface - hence the angle of attack of the elevator is reduced (by the aircraft’s pitch attitude). More backward pressure is required to continue the rotation rate. After lift off, once clear of the ground, the airflow over the tail is restored to its normal direction - hence less back pressure is then needed.