Do you have a source for that?
I just consulted an online dictionary, a printed dictionary, a second printed dictionary, a Latin dictionary (because hybrid is a Latin word), and wikipedia.
The online dictionary says, "the offspring of two animals or plants of different breeds, varieties...
The word "hybrid" is used both ways, for crossing between breeds or between species.
Examples of crossing breeds within a species would be hybrid corn, hybrid layers like OP has, and so forth.