I think people mix "smart" and trainability. A dog can be smart and a great problem solver, but getting them to do a bunch of complex things on cue might not be their forte.
A working breed was bred for the trainability aspect, they want to do what they are told, they need to please. It is in their nature to do so. That is why the breed is placed in the Working Dog class.
Most pro's in turn have a con and vice versa. Not being as trainable as the considered most trainable breeds is not a negative per se, unless you are going for a SCH title, then you might be in for some frustration.