The rear bracket is changed because of 2 reasons.
1: from the 2 holes in the old bracket, only the outer holes were usable, the inner hole on the brake side, would bind the upper camber link.
now the holes are above each other, to be able to change the rear roll center, and camber rise.
2: As you can see, the middle part of the bracket, is made a bit higher, this is to prevent the T-bracket of the rear body mount (#903536) to come lose in case you flip the car on it's roof.