I am not saying that there were not a few St.John's Dogs in obscure areas that were very similar to some of today's Labradors in Type. Considering the diverse population, there likely were...but there were apparently many many more of widely varying characteristics within the same "breed": lanky, stout, small, large, short-coated, long-coated, otter tail, feathered tail, curled tail, straight tail, broad head, narrow head, light eye, dark eye, whole colored, brindled, thick coated, thin coated, etc, etc, etc, etc...
De Boilieu clearly stated that these diverse dogs were of the same breed. What he considered representative or "true" in his opinion was indeed the "dog having smooth, short hair, very close and compact to the body." That does not eliminate the clear statement about the long hair-variety being the same breed.
"There is the smooth-coated dog of the same family, and as useful an adept. The flat and shaggy, and the smooth-coated—I mean as short in the hair as a Mastiff—are sometimes found in one litter, and one of the best I ever saw was thus bred from Mr. Drax’s keeper’s old “Dinah” (imported), the father being also…”
The Dog 1872
This is a later quote from Great Britain which only confirms the dilution of St. John's waterdog genes once they arrived in England, in my opinion.
Except the litter here described is from imports, not the crossbred animals of the gamekeepers in the UK. This is a description of a litter of St. John's Dogs, not the later Labradors.
Here are the points you missed in this passage that point to an animal that is pretty different than the romanticized St. John's Dog.
"Newfoundland is one of the worst places in the world for getting a good, or at least good-looking Newfoundland dog. In St. John’s and its neighborhood they are the most ill-looking set of mongrels that can be conceived. In the more distant ports however, the breed is better preserved. A thin, short-haired black dog belonging to George Harvey came off to us today. This animal was of a breed different from what we understand by the term Newfoundland in England. He had a thin tapering snout, a long thin tail, and a rather thin but powerful legs, with a lank body, the hair short and smooth. These are the most abundant dogs of the country, the long-haired curly dogs being comparatively rare. They are by no means handsome, but are generally more intelligent and useful than the others.
Excursions in and about Newfoundland 1839