Dry brine recipe does not mention rinsing bird after 3 days. Did they mistakenly skip this step or is it not necessary when dry brining?

No, you read that right -- rinsing isn't necessary. The amount of salt is very moderate (not much more than you would use if you were salting the bird just before roasting). It should be absorbed into the flesh by the end of 3 days. Plus, the last stage of air-drying the turkey in the fridge is to help the skin crisp -- you wouldn't want to get in the way of that by rinsing.

You will not need to rinse the bird. The salt will not longer be visible on the skin of the turkey. Simply pat dry and roast.