It's possible that you heard or saw something about a hybrid. I'm fiercely opposed to such things, but there are "those" who experiment & have managed to
breed such things as "jungle corns" (a hybrid corn & king snake) so I'd not be surprised (only sad & angry) if they've done the same thing with a corn & bull snake.
Nature ("natural selection") gets it right, IMO...humans just mess things up for profit, novelty and showing off.