Gut-loaded means that the prey item is fed well, so that the predator will be able to receive those nutrients in the most natural way possible. Like pasture-fed organic beef in your hamburger. There's a lot of preservatives and filler in pellets that frogs aren't supposed to have. That's why a variety of foods is suggested. Nothing is absolutely complete, except the diet they eat naturally.
I've seen a frog kick a guppy in half because it was too big, and he couldn't swallow it.
I actually saw some plastic canvas betta hammocks on here, and decided to add one to the plastic canvas lid on the frog tank, since they have to surface breathe also, and they occasionally have trouble floating at the surface wherever the plants aren't filled in. I'll post a picture when I'm done!