A drug addiction is different from hoarding, but can be seen in many cases. The problem with  meth is that it makes the brain think it is extra smart. The hands and mind need to be busy to keep up with the increased brain activity. Unfortunately my ex wife became addicted to meth, and she explained how productive she though she was being, but in reality she was making messes of everything. She would dump out all of the drawers in our bedroom for several nights in a row, then organize it all again. She would shampoo our carpets at 2:00am, and would take pictures off the wall, just to paint the frames a different color. Meth changes the normal thinking of the brain and kicks it into high gear, so the homes you are seeing are being filled with "projects" most likely. Without the true hoarding disorder, the attachment to the items probably is not as great if present at all and if the addict goes to treatment, their sobriety would most likely allow them to let go of all their "stuff".

The bottom line is that drugs change our brain function and as such change out behavior. It really can't surprise us to see hoarding in a home of a drug addict or alcoholic which is just as common, especially if depression is the cause of the drug use or alcohol. Depression is a big factor in hoarding as well as escaping with drugs and alcohol so we can't be surprised if we see both hoarding and drugs/alcohol together. Hope that helps!