"No offense, but you seem kind of snobby about the whole 'dogs guarding animals' thing" Your St Bernard is guarding TERRITORY LGD's guard ANIMALS
Okay, that MIGHT be true. But functionally, on a small farm or backyard flock, what the heck is the difference? You're saying it's not worth the trouble to have a dog trained to guard who also won't mess with chickens. To me, it's very much worth the trouble, and my property IS fenced. If he is actively going to check on them, and responds to them being in distress(not out of "curiosity" as you say, he goes into full blown war mode ready to kill whatever has invaded his turf, then how is that any different? The ONLY difference I can see is that a LGD lives with their animals in open terrain.
Note, I'm not saying that my saint bernard is a LGD, I'm saying he is capable of doing the job that you keep saying his breed(or any others that aren't an 'official' LGD breed) can't do, which is guard a backyard flock of chickens, if not intentionally, then effectively, by both deterring and destroying predators of said birds.
He is capable of the following:
-Actively responding to any sound out of place
-Eradicating threats and or predators with extreme prejudice
-Being large enough to successfully take out said predators.
-Being friendly towards, and respectful of the chickens as part of his pack
-Respecting me as alpha and following any specific commands I give him
-Keeping human threats off of and away from my property by his sheer bulk and mannerisms(He will charge the fence, snarling, at ANYONE he doesn't know well)
-Being calm and gentle with our family, other pets, and well known friends, whom are free to come and go and do whatever they please and he won't even bat an eyelash.
It matters little what y0ou can TRAIN a dog to do .LGD's guard by INSTINCT, and a German Shepherd is NOT an LGD
Also, if it matters to you, I did NOT train Yoshi to do what he does. He is a naturally protective dog. He IS a well trained dog, in that he knows many tricks and commands, is house trained, and walks perfectly on a leash without pulling me, but I did not teach him any of his guarding behaviors. He does patrols and checks up on everyone in the family of his own volition. He's aggressive towards strangers because he wants to be, and I see no need to end such a desirable behavior, when you never know what sort of people could come knocking at your front gate.
So maybe he is just an anomoly, but you have to remember, all dogs and dog breeds had to start somewhere, that instinct had to come from somewhere, in order for it to be molded into the behaviors and instinct we know today. So please, don't discount another breed just because it's not some chosen and special "LGD" breed. They are all dogs, and they are all amazing creatures in their own right, and some of them can amaze you with just how out of character they can be for their breeds stereotype.