You only need to install the rear adjustable bushes, if you have bad uneven rear tyre wear from excessive negative camber / toe wearing the inner edges of the tyres out.
If your rear tyres are wearing fairly evenly across the tyre, then it'll be a waste of time / money getting them fitted with the car at standard ride height.
Some cars are better / worse than others of the same model.
I'd just hold off fitting the adjustable bushes and drive the car for a few thousand kms and see how the rear tyres actually wear.
Then you can make an informed decision if the adjustable bushes are required or not.