Exactly what I've thought whenever I've come across the 'tester-fooling' theories; I mean, if Reckitt Benckiser themselves can't even blend codeine and ibuprofen in a pill without problems (see Nurofen Plus), what chance does a more clandestine lab have? You'd expect massive variation from pill to pill at the very least.
Still, Occam's razor doesn't apply here it seems. So the lizard men and the Rockefellers continue to mix up the trojan horse pills, fooling the testers and scamming the kids.
Makes a good read though, must admit.