I think this is probably the bigger value. You are going to be much better thought out before you undertake a path that is hard to bail on. If it were free, you'd see the first year class full of dabblers, folks who are just going to give it a try for a year or two to see if they like it, and then bail. Folks will go to med school simply because they "ran out" of college. Essentially what you see going on in the lower tier law schools. Classes will be full of folks who really don't want to be there, and who will quit at the first sign of adversity. Not the folks you want in med school. These are the folks you screen out when you create a barrier to quitting.
The article is based on the assumption that there are lots of people who don't go into primary care because the income isn't high enough to service the debt. I think that to take that stance, you had better be sure that folks aren't shunning the primary care fields for totally different reasons than money. Honestly, with the average pediatrician earning about $140k which is enough to service a fair amount of tuition debt, and with primary residencies shorter than most of the specialties, I don't really think it's all about the money. I mean according to a recent survey, orthopedics is on the other extreme from peds, with the highest average salary, of about $350k, but yet I know of no orthopedists who ever said, "you know, if it weren't for the money, I would have done peds". Money is but one of many factors folks use in choosing careers, and outside of pre-allo it usually isn't the most important factor.