Heroin hasn't been marketed as "virtually non-addicting" or actually non-addicting for quite some time, although that's pretty much the exact tagline it had when it first came out. It doesn't take a genius to see that marketing something so incredibly addictive as OxyContin as non-addictive will lead people to take it and get addicted unnecessarily, regardless of any other circumstances. It's simply impossible that this was a mistake. I can buy it may have been a mistake in the late 1800's when heroin first came to market, but in modern times, this was a calculated effort to make money off of people's misery and deaths. "People will die and their lives will be ruined, but we'll make a ton of money off them, so fuck them," is likely what was said before going ahead with this plan.
This was pushed by doctors at the behest of the companies, doctors who the patients trusted had their best intentions in mind. The drug companies knew from history that the US government would not do anything to stop them, but instead would help to promote their drugs over the illicit substances sold on the street that had the exact same effect. To claim that all the advertising, pushing, and money spent on promoting OxyContin had no effect on anyone and that people would have taken heroin regardless without being pushed by the drug companies' machine into first taking something they claimed was benign is fucking absurd and flies in the face of both logic and current research in psychology, advertising, and marketing.