Exactly, there is no breed registry for chickens like there is for dogs/cows/horses/sheep/pigs/etc. At shows, they judge the bird based on SOP alone. If it looks, feels, acts like X breed, it is. Take a look at Greenfire Farms "Lamona". They have stock from a guy who took the original formula...
If you are looking into working with a breed long term, I would join a Facebook group (or 5) specifically for the breed(s) you are considering. That is where the show breeders are and that is where I found my breeding stock.
For example, I bought a trio of second best LF Dark Cornish from a show breeder for $150 in the fall of 2017, I hatched 40+ chicks off them this past year and I am SPOILED for choice when it comes to this year's breeders. At least half the pullets look to be VERY good and the cockerels are all...
You could work with hatchery stock and work them up to standard. However, it will probably take a good many years of work to do it with little return on your investment.... except for a LOT of cockerels in the freezer and $5-15 (depending on where you live) for each point of lay pullet you...