The nitrate level will not keep on rising indefinitely. As long as there are regular water changes done it will settle out at an ultimate value.
In the case mentioned above, at 1ppm per day with weekly 20% water changes, the nitrate level will settle out at approx 30ppm after a water change rising to approx 37ppm just before the next change. It will take 20 water changes at least before this level is reached.
eg 30+7 =37, 37*0.8 = 29.6 (approx 30) and repeats from here.
Haven't read the article yet but if its incorrect or just unclear, an amendment could easily be added in the next AW. I'll even volunteer to write it!!