In the manga / Brotherhood, we learn that the reason human transmutation is forbidden is because it would otherwise allow people to create their own private armies (at least according to the man who talks to General Armstrong after she's transferred to Central). Right after that, we're shown the mannequin "soldiers", implying that they're the results of some form of human transmutation.
But it's pretty obvious that the mannequins are different from the products produced by Ed, Al, Izumi Curtis, and Roy when they attempt (or are forced to attempt) human transmutation - in the case of the mannequins, the transmutation has actually produced what the alchemist probably wanted and is "successful".
Given this, what's the difference between the human transmutation referred to in the context of the mannequins and human transmutation as attempted by the sacrifices? Is the difference in result simply an issue of having a different intended result and/or maybe philosopher's stones, or is there potentially a different explanation for this?