they make a distinction between 'kinds' and 'species'
the original kind had all sorts of genetic diversity that you could then breed out to get a very specific set of traits
there was a dog 'kind' from which we get wolves, coyotes, toy poodles and spaniels
but they are still dogs and no matter how much you breed them, you won't get a cat
all sorts of dog breeds don't mix, but we don't call them a different species like they did with those birds
they would say we are adding no new genetic materials, just creating creating new combinations of existing genes, which has inherent limits unless you go to artificial means (gene splicing, etc)