A motion ratio change has a huge effect on the suspension wheel rate, which is all you care about, as the wheel rate is what the car's tires actually see, and not the spring rate. That is the effective spring force that the tire sees as it is translated from the spring to the tire by the suspension geometry. The spring is compressed as the wheel moves up by a lesser ratio called the motion ratio. If the motion ratio is 0.8 in one case, then if the wheel moves up 1", the spring compresses by only 0.8" which is how the motion ratio is defined: measure spring and wheel displacement and divide one distance by the other. But since spring rate is in lbs per inch, it means that the force at the spring is 0.8" times the spring rate, which we might assume is 1000 lb/in for an example. Thus moving the spring by 0.8" x 1000 lb/in gives a force at the spring of 800 lbs. The force at the wheel is reduced by the motion ratio, so it is 0.8 x 800 lbs or 640 lbs. The wheel rate is thus 640 lbs/in, which is the spring rate if 1000 lbs/in x motion ratio squared. Motion ratio is super important because the force at the wheel is dependant on the motion ratio squared.
Now make a geometry change in the lower arm which changes the motion ratio to 0.7 for example. Assuming the spring is the same at 1000 lbs/in, the new wheel rate is 1000 x 0.7^2 = 490 lbs/in compared to 640 lbs/in before. That is a very, very large reduction in % terms as the wheel rate has gone down by 150 lbs/in or 150/640 x 100% = 23%. That is a lot! It is like changing your springs from 1000 lbs/in down to 770 lbs/in.
So if you use springs and dampers tuned for a 0.8 motion ratio, they will not be correct (not even remotely) for a 0.7 motion ratio suspension.
Now I just used some random numbers as an example, as I don't know the GT-R's CBA and DBA motion ratio values, but if I was changing dampers and springs from CBA to DBA values, I would absolutely change the control arms to get the motion ratio those components were designed for.