They do not sell completely random mixes.
Some of the "breeds" they sell are mixes, but specially planned by a breeder or hatchery to give certain results (all colors of sexlinks are mixes done in specific ways to be color-sexable as chicks, some Olive Eggers are mixes of blue-egg breeds with breeds that lay dark brown eggs, many of the meat-type birds are hybrids of one sort or another, etc.)
I think the chicken in the first post is probably a Cream Legbar. If not that, she is probably an Easter Egger or an Olive Egger (some EEs and some OEs are descended from Cream Legbars, and can look quite a lot like them.)