I've seen exul on lists, and probably seen them at an importer's. With a lot of Hemichromis, you can only be sure what you're seeing if you know their exact provenance, and unless you get them from friends you trust, that means wild fish from very reputable importers. For a long time, lifallili was the sought after one, and lots of jewel group fish were sold under that name because their rep was as less aggressive and smaller too. I got the real thing once and other species twice.
My problem with every Hemichromis I've bred is that no one wants the fry, and man, they produce fry. The babies are actually quite pretty from the get go, but the aggressive nature of the fish shuts down sales. They are easy fish to manage in large aquariums, but at one pair per tank, that quickly becomes a lot of space and money devoted to them.
Somehow, one lake on a vast continent has become the source of all "African Cichlids" in the minds of inexperienced aquarists, and while Lake Malawi mbunas are cool, their keeping is radically different from the far more interesting Cichlid species that occur elsewhere on the continent.
trivia - the supposed common jewel is Hemichromis bimaculatus, and odds are, that fish has never been kept in aquariums. It was a misidentification from the start. But my limited experience with the group (I have bred 4 species and kept 7) says they are all pretty adaptable, and similar in their needs. Some need bigger tanks than others, due to their size, but as long as the tanks are large enough for you to manage their fierceness, just add water and get ready for thousands of babies no one will buy.
You're 100% correct - I've bred traditional jewels. 
