Adding Water Question

I'm an All-Grain brewer, and I'm having one small difficulty with Beersmith and I am hoping you all can help me out.

I batch sparge, so I pick the profile Single Infusion, Full Body, Batch Sparge, however every time I brew I get something similar to:

Mash In: Add 21.56qt of water at 161.7F
Batch Sparge with 2 steps(Drain mash tun, 2.91gal) of 168F water
Add water to achieve boil volume of 6.58gal.

The part I don't understand is, why am I adding water to achieve the boil volume; why isn't the water needed to reach that volume rolled into one of the other two steps??

Thanks in advance!

In all liklihood you will not need to add water. That is a generic step to ensure you have he right preboil kettle volume. Sometimes grain can absorb more water than is typical.  In that case you might need to add a little bit of water. In most cases I have a little more water than I need.