The quick answer is no, grain-free diets are not the cause of taurine deficiencies in Golden Retrievers or any other dog…kibble is.
I just read this supposed “study” on how diets high in legumes and potatoes can cause taurine deficiencies in dogs and cats and that part is very true. Both, dogs and cats are carnivores, therefore, their bodies are designed to eat meat, therefore, their bodies are designed to get the necessary amino acids, such as taurine, from their food. Dogs can produce their own taurine, however, if their food is not providing a substantial amount of meats that can help their body produce taurine, then yes, they will have some problems.
The biggest problem with all pet food is that we cook it to death and feed it to our carnivores who are designed to eat and get all they need from RAW meat. We have been causing kidney disease, diabetes and hyperthyroid disease in our cats for years due to feeding our feline friends biologically inappropriate diets containing lots of plant matter and very little, very overcooked meat biscuits. Now dogs, who can normally produce their own taurine, are suddenly not able to. That sort of evolution doesn’t happen over night or even in a few years since grain-free food has been a big thing. It evolves over a long period of time, say about 100 years, since we started feeding kibble?
None of this surprises me, in the least and just because “many of the dog is were eating a grain-free diet” during this study, doesn’t mean that that is the problem. If you want to keep your dog healthy, supplement (at least) with raw bones, chicken or turkey necks and other raw and freeze-dried raw treats and feed a high quality kibble with meat as the first 5 ingredients.