So we've noticed some curious properties of Ghestal Greens while doing experiments with Chocobo feeding. Apparently, although these greens are the most common, various forms of Chocobos will eat these more readily than the better tasting other varieties. But why would a chocobo pass up one of the greatest treats for a simple meager meal.
We think we know why! The Chocobo is a creature strong in habits, and it does not like to do new things. That's one reason we don't have any yellow Chocobos hurting themselves by trying to climb up mountains. The regular choco is used to the color, texture, and smell of regular greens - and so would prefer them at first. We did find, however, that if provided the better greens often enough, Chocobo might develop an over appetite for these greens and not accept anything less, making it difficult to feed.