I don't know if my experience with a similar issue on a car applies, but here goes.
After the alignment the tires continued to wear in the same spot. A front end tech told me that once a wear pattern develops on a front tire that it will continue to wear the same way, an alignment will not stop the pattern. My one data point supported his statement. The tires in this case had a significant pattern, and it was a car.
I agree with Gary, if the pattern is pronounced, I would swap them to ensure the largest safety margin possible on the front. Knowing that swapping tires is not something you do in the driveway, I would carefully measure the fronts across the width of the tire and record those tread depths. Drive it for a couple of thousand miles and remeasure. If they are wearing evenly based on your first measurements, then my theory is baloney.
Richard, Rhonda, Ty, and Alex
1995 Newell, 470HP Detroit Diesel Series 60