Looking at the pictures above, it seems like the front one, with those elliptical washers and reinforcing berm of material on the one side of them maybe gets more stress or compression, perhaps from the direct torque of the transmission, than the rear one does.


Obviously just naive conjecture, but there's must be some good reason for the differences. The front one is more expensive than the rear as well so there may also be structural or other differences that are not apparent or visible.