It doesn't mater what the Gh of the city water is. His water softener will remove most of it. his test strips read in ppm. 1 degrees 17.8 ppm. so zero degree water wcanstill have quite a bit of GH. 0ppm no GH is not good.
I can't find any reference to water softeners in this thread, except the two citations you quoted. I guess they are from another thread? Same OP, so one would assume the same issue (water softener).
That leaves the question, what is the GH of the water pre-softener? Whether city water or well.