Is it redundant to use butter milk in a sour dough recipe?

A ) Could that be over doing the sour?

B ) Because the buttermilk acidity is sort of a dough conditioner, does the sourdough culture do that too in addition to leavening the bread?

C ) In 100% Whole grain bread might all the above be a good thing?

Is it better to put a higher percentage of starter in whole grain bread. Whole Grain....for me, that means no white flour.

If so, how much more? and thank you for your time.

Ron