Catalytic converters are also stolen for making the drug _bombé_: https://www.spiegel.de/international/world/new-drug-in-the-d...
The article does suggest that bombé is made from conventional drugs and basically cut with converter residue, so perhaps the residue slightly modifies its chemistry. Or it might do nothing at all; I'd be surprised if there's been a blind study comparing the effects of bombé made with cat residue to the same made with, say, clay.
But it's still rare metals thieves are after so I assume the substance abuse popularity may grow outside Congo.
A bit how pine/coal tar was used to make just about every chemical 100 years ago.