I agree that you should be sure of your facts before you advocate for a change.... however I also know from experience with the system that it is sometimes very hard for a kid (who is only 18) to advocate in the system. He is seen as a drug addict, who has not succeeded in the past and they can languish in the wrong place.
Fact is even if he has been in treatment before being in treatment again can help and being in a better fitting place may make a difference in his success.
And I think having parent and family support makes a difference.
I think as long as he is wanting treatment and isnt just trying to get out of there showing your support is a good thing.
TL