First of all, the poultry genetics corporations like HyLine, ISA, Warren, Hubbard, Tetra, etc, make dozens of "models" of red sex links for the commercial brown egg industry. They sell millions, perhaps billions of these each year for world wide consumption. Each of these companies make a few different "versions" of the red sex link. Again, the male used is has gold genes and the female used has silver/white genes. This is how the chicks are sexed at hatched. This cross makes the male chicks white and the female chicks buff colored. This is a HUGE cost savings of being able to sort these chicks for an industry that only needs hens. The cockerels are largely just destroyed and the protein used in cat food, plant food, etc.
The smaller retail hatcheries such as Cackle, etc can either make their own sexlinks or buy the parent stock from the large corporations. These smaller, Cackle type, retail hatcheries produce thousands of chicks for direct sales, not millions of chicks such as a Hyline commercial hatchery would.
These smaller hatcheries can use a few different red roosters. As long as it has the gold gene. Such as a hatchery RIR, a hatchery New Hampshire or a hatchery production red bird of some kind. For the silver/white female side they can use whatever they have. So called RIW, Del, silver Leghorn, silver gene Rocks, etc. Just remember that none of the parents are standard bred examples of their "breed" and wouldn't ever qualify to enter a poultry show.
Few of the hatcheries are going to disclose the true, pedigree of the parent stock anyhow. It is easy enough for them to make several different models of these red sex links and sell them under whatever name they wish. Kind of a Labra-Cocker-Peka-Doodle. If you wish to know with more precision, and base a purchasing decision based on more precise information, that quest is ill fated, I'm sorry to say. Hatcheries often don't say and if they do say for marketing purposes, the information given is highly suspect and unverifiable.
Go by previous customer feedback. That's about all one can do. Since backyard chicken keepers really want females, these birds are popular. They are sexed. A huge plus for folk's who don't want or can't have roosters. They are people friendly, as a rule and lay up a storm. Very popular.
Hatcheries rarely, if ever, have ANY birds that a pure bred, or bred to standard. Their niche is volume, cheap, available and healthy. That's it. It you want standard bred poultry, you have get those from a breeder.