User blog comment:BannedLagiacrus/Monster Appreciation Week: Great Jaggi(4th Gen)/@comment-9290318-20150301214202/@comment-4702773-20150302152238

I believe it is because they are high in protein. Herbivores like Aptonoth possess layers of fat that don't really serve much purpose to a carnivore. But since GJ's are basically all muscle, while still being weak enough to be easy pickings for a Jho, it would be the perfect meal.