It's true, a few grains here or there make no difference.
But, here is how I do it:
I build 6-12 arrows at a time, I weigh all my inserts, nocks, shafts individually, take the one with the lowest weight and set it aside, I then dremmel the rest to match the weight exactly. I do the same with the shafts, I use the ASD to make sure each shaft is identical in weight, then I build them.
That is why my completed arrows usually end up about 3 grains less than ones that are built using all the parts and trusting they are the same.
Does it help accuracy? Nope, not as far as the equipment goes, but it does a lot for my confidence, I hate missing.