There appears to be genuine disagreement over the authenticity of one piece shell belts.
Some folks allege it can't be done, at least not with hides from Horween.
I don't have a dog in this fight, so I don't really care. I'd be glad to hear from a shell belt expert, if there is such a thing.
This is not a knock on AE belts. I have plenty (calf), and am wearing one riight now.
Economically, shell belts would seem to have to be made from the remnants of shell hides after shoes are made. This appears to be how wallets, key fobs, etc are made. It seems unlikely to me that you would be able to get a single strip leather long enough for a full belt.