Here is why..
The plates are drilled/reamed as a stack-up assembly to pretty close tolerance. ANY angular irregularity would cause problems if the stack-up is not in the same orientation as it was drilled. My -4 plates also had 2 of the holes in a first oversize condition, and also had oversize bolts supplied. I found when assembling mine, it is best to get everything in place using about 8 cheap bolts from hardware store that are not close tolerance and leave them hand tight, then install the kit supplied bolts carefully and get all of them in before installing any of the nuts. I used an assembly paste grease that is anti-corrosive and aids in the bolt installation while gently taping them through with a plastic hammer. Just be carefully there are no burrs or debris in the parts putting them together...