Whether you buy into it or not it can happen, and does happen, and still does in the wild. I've even had it happen to a flowerhorn with it's tankmate. Not to say it frequently happens, it doesn't, but if you want to be completely risk free of that (of which your odds are going up since you are using them as feeders) it is something to note. Since you have experience with blue gill, you should note their defensive reaction when you catch them is to stick up their spines, and furthermore the predator you are talking about is a bass which tend to have much larger mouths. Imagine spines and a smaller mouth fish, now it doesn't always turn out pretty. Just posting from experience.