Seems like tolerance isn't really an actual problem here.
Are you suggesting these parents have some course of action to cure their child's problems? The child could relapse, but I don't understand what point you're trying to make.
What rubs me the wrong way about this article is that it's written in such a way that any parent whose kid has a problem with tantrums might think, "hm, what if I just drugged up Johnny?"
That is not at all clear from the article. There is no talk of withdrawal. If you take away pain meds and the pain comes back, that is not withdrawal!
OTOH, these specific parents, I can't even imagine what they're going through. My heart goes out to them. A child like this would be so difficult to raise & to help, and obviously they have so much love & dedication just for their willingness to stick it out, I'm so glad a little THC works for them, as opposed to having nothing that works, or some other pharma cocktail that "solves" the problem through vegitating the kid's brain. Anything that gives them a semi-normal existence has to be a Godsend.