It's possible tho. I have a pekingese who sleeps most of the time and is pretty lazy. These original purpose of this breed was to be a companion for chinese noblewomen. Last year I was on vacation and the house I stayed in was on a tiny farm surrounded by a fence. From day 1 until I left my tiny, lazy dog turned into a tiny version of a guard dog, warning me of "intruders" aka neighboors walking past the fence and then following them while barking loudly. She never did this at home and after the vacation was over she returned to her old self. It was weird, man. Adorable but weird.
If a Pekingese can be a guard dog, the tranch dogs who are bigger and stronger can too...but the tranchers would have to make the effort to train them...which of course they won't.
This going to get a little spergy, I'm sorry in advance.
Massad Ayoob talked about this a lot in his book The Truth About Self Protection. A lot of stuff in that book is pretty dated but this stuff is still pretty good. Not a lot of room for development left in scary black tactical assault puppers.
Ayoob thought of four levels of training for dogs. An alarm dog, a protection dog, an attack dog, and a guard dog.
Most dogs are natural alarm dogs, all that's needed is that the dog barks at unfamiliar people, even if all it will do is bark. Many dogs will also naturally intervene in physical confrontations, meeting the standard of a protection dog. Most dogs can be a protection dog with basic obedience.
Attack dogs are dogs that are specifically trained to attack on command. There's a whole lot more here than just a dog that will sic when you tell him, but also training commands for where the bite is going to be, various desired behaviors leading up to the bite, and disengaging on command. Attack dog training can also encompass things like ignoring gunfire, pain, and other dogs. Most police, military, and civilian dogs who do advanced training are at this level.
A guard dog is a dog trained to attack anyone but it's handler. There are no pet guard dogs, or at least there wouldn't be in a sane world. These are the dogs who you train abusively until they will rip out the throats of anyone who isn't explicitly made the master of that abuse.
IIRC they bought the dogs to be livestock dogs, before immediately demonstrating that they don't know what livestock dogs are supposed to do, let alone how to train one to do it.
The Tranch dogs are definitely good alarms and are probably reliable protectors for most confrontations, based on breed alone. I wouldn't rely on them to charge through gunfire and fight through injury, which is probably how the tranchers view them as of late.