I know this thread is older and not super active but in case future folks are interested in legbars as well, here's my 2 cents as someone beginning a breeding program:
The breed is relatively new to the US and GFF is the primary importer. That doesn't mean you should run to them for birds. What it does mean is the vast majority of cream legbars in the country are from the lines they brought over (or some combination). GFF doesn't necessarily breed to the standard any more than any other hatchery. They just import rare breeds. Breeders then still have to refine to the standard.
Speaking of standards, there is only a proposed standard and it is still subject to change. Showing them is good for getting the word out but "show lines" are essentially somebody's guess of what 1) the final standard will be and 2) how judges will interpret it. It's great to work on the breed to improve it here but nobody has champion CLs. They have CLs they've bred to their interpretation of a proposed standard and they hope a judge would agree.
My personal experience has been interesting. There are a couple breeders in my general area, plus 2 hatcheries within driving distance that offer CLs. I've grown out chicks from 3 separate sources for genetic diversity. Those closest to the proposed standard, with cream coloring and good legbar shape, are from a small hatchery. If anyone wants to know which one, feel free to message me. I did get one CL from Meyer in a rare assortment. She's a joy with great egg color but is too gold and will be in our layer coop rather than breeding. I don't know how representative she is of their CLs generally. Tiny sample.. They're expensive at Meyer so you'd hope for better quality. All considered, I certainly wouldn't dismiss every hatchery CL in the country. Most of us have only seen small samples and even the best show breeders might only get a few great ones out of every hundred birds.
Lastly, do your research thoroughly on the breed. Some "show" lines have had issues with chicks not being sexable at hatch. To me, visually sexable chicks are a key part of the breed. Lines that don't keep that trait do damage to the genetic pool for the breed, in my opinion, and should be avoided no matter how great they might be to show.
Good luck to anyone looking to add legbars. They're our favorites.