The ginger powder is there, along with the ascorbic acid (Vitamin C) to
enhance the dough - like Lora Brody's Dough Enhancer that KA sells. So I
think that the creator of the recipe wanted them there for a reason - to
give the dough a specific consistency or to give the crumb a certain
flakiness or to make the bread keep better.
You could try the bread without the ginger and see what it really does.
I have a dough enhancer recipe that includes ginger powder in it along with
the Vitamin C and some diastatic malt powder and acid whey powder (that KA
no longer sells).
I used to use the enhancer a lot, in doughs that had no egg in it. I
haven't really used it in awhile. It seems to help with ABM loaves a lot.
If you aren't making the bread in an ABM I would think you wouldn't need it.
Make the bread without it and see what happens.
Ginger is easy to find if you don't have any. They sell it in the
supermarket. I buy it in quantity through either Penzey's or an Indian
spice shop I go to.
RisaG