Just published this video on what bugs you can feed to a cham:
BBFs or GBFs, or really any Blow Fly (Carrion Fly) are actually pretty healthy, much higher than 6/10, they have high protein, decent calcium, and most importantly! They are about the only feeder that we use that has Preformed Vit A. GBF/BBFs, are Carrion Flies, the Maggots before you get them, are raised on Rotting Decaying meat. This sounds gross, and thats why people dont try to breed them lol.
HOWEVER, Carrion flies, are shown to make up 20-30% of Wild Chams diets. They are a HUGE part of Wild Chameleon diets, and how Chams likely get their Vit A in the wild. As to gutloading the flies, they actually can be gutloaded, which BSFs cannot. The Flies in the wild, eat Nectar and rotting fruit, sweet things. They will do the same in Captivity, so Bee Pollen, with some water to make a syrup, will be consumed and is a great gut load. On the Contrary BSFs, have no moving mouth parts, they do not and cannot eat, only drink water.
I'm not sure why they are rarer in the Reptile hobby, and they kind of are, but that is because your looking in the wrong place. Its more than likely, because most reptiles cannot eat them. A bearded dragon or a Leo, cannot catch and consume a Bottle Fly, Chameleons can, Frogs can, Mantids can, and places that specialize in feeders for one of those 3, will have them. There is also the fact, that many are grossed out by the fact that Blow Fly, larvae are actual maggots. House Flys (of which Bottle flys are also frequently pests in your house) are also carrion flys. Their larvae, is the actual definition of Maggots, that feed on nasty rotting decaying meat. However aside from the specialty shops I mentioned, another great resource for them, is Bait Shops. People love fishing with BBF/GBF Spikes, and the flies, they are used for fly fishing. They are raised on rotting and decaying meat, but so is Josh's, thats the only way to raise them.
Most of the stuff, that is touted as a Chameleon feeder, is not even eaten in the wild. They eat Bees, Wasps, Beetles, and Flies, occasionally Hoppers, Snails, Sticks, Mantids (which eat flies, the only Mantid a panther would have access to is Ghosts and Gambits, AFAIK, both of which only eat bottle flies) Sticks, Katydids, ect. Never would a Chameleon in the wild, eat a Roach, or Hornworm, a Super, or a Silkworm. They are either not where chameleons are, or like roaches, they are ground dwelling nocturnal insects. Geckos eat roaches, not Chams.
As to whether, that matters IDK. However I do know, from that post recently that Nosy Bes, kept as captives, usually dont have the Yellow Lips, Brodys does and he feeds a ton of WC flying insects and thinks that is why. We would need testing, but Brody and Petr Nectas think that is why, if it is, it shows that something is missing. I am not saying we should limit feeders to what chams eat in the wild, just that detracting from natural foods while promoting unnatural ones, might be a bad idea.
Also, if you think about it (Because I just did lol, as checking my chams feeder cup) the entire invention of a feeder cup, is so that we could defy nature.
We use feeder cups, to feed worms, roaches, crickets, larvae, however in reality that issue is made by us. The insects that chams eat, dont stay on the ground, they dont hide. The hoppers they consume are not noctural like crickets, the flies fly, the bees fly, the beetles fly and climb. We have litteraly went out of our way, to defy nature.