Iirc, they haven't used St Bernards for their original purpose since the late 1800s or early 1900s. After the darn Victorians got to them and did their usual kennel clubbin' pure breedin' shenanigans, the modern dogs are nothing like the original rescue dogs, which were smaller and more varied (and tbh the modern dogs would be pretty crap at the job). Back when the dogs were originally used, and before the newfies were brought in to help save the breed after avalanches killed a bunch of them, the monks didn't use a proper stud book or anything like that. They kinda just let the best workers breed, no matter how they looked.