We are currently in the process of migrating from the use of "addictiveness potential" to "abuse and dependence potential", as the current format leaves too much room for subjective judgment. So something like oxycodone and similar opioids would be classified as "produces dependence and has high abuse potential" instead of "x amount of addictive".
The Heroin page is protected by edits from non-admins to prevent malicious edits that might endanger users. If you can send me the text you were gonna put for it, I'd be more than happy to put it in for you.
Thanks for the recent legality edits, by the way. They look good!