OperatorEntityMotion calculates the motion of player entities based on the difference in position between two ticks without applying the AddMotion multiplier that is applied to the motion of other entities.
Suggested fix:
PieceOperatorEntityMotion.java, line 51
Replace
Vector3 vec = Vector3.fromEntity(e).sub(last);
With
Vector3 vec = Vector3.fromEntity(e).sub(last).multiply(1.0 / PieceTrickAddMotion.MULTIPLIER);