When did they start that?
Kelly, Young and Walker went there, not because then NFKL didn't want them, but for better pay.
Since then, all of these come and go incarnations of USFL/XFL/whatever almost exclusively have filled their rosters with guy s who couldn't get drafted or stay on a roster. Why do people endlessly claim that each new iteration will be a great developmental league for the NFL? It's not based in any reality---over decades. This has never been true. It's just mediocre to bad football that dies of fan disinterest. The new UFL is absolute proof of this failed concept.