Yeah, it seems fishy. If 6 reps of something is difficult enough to do such that it has in impact on muscle growth, I can't see how they could manage 30 reps of the same thing. I wonder if the 6 reps 5 days people were untrained, while the 1 set of 30 people could manage it because they were trained enough so that it was possible (and therefore too easy)? Or maybe the 1 set of 30 was with a lighter weight to make it possible?